Are you sure this isn't just the onset of schizophrenia? I mean from 1998 to 2017 thats 19 years somebody or a group of people want to bleep with you. Nobody would follow you through 19 years for the laughs...unless they're psychotic. I'm kidding about you being schizophrenic but the way the situation is described to me from experience with peoples psychology makes me go there. I'm not so much kidding about an actual psychotic individual harassing you for 19 years. I'm going to use a psycho person being the root of the harassment analogy because the question is who is doing it and how.I could suggest covering some bases that is like a total overhaul of your cyber life but necessary in a situation like this if you're not joking. This recommendation is full blown paranoid panic mode. I'm talking like cleaning house paranoid mode.
You can't be hacked and loose personal information if you aren't using devices that are infected. To be sure you're all secure you need to be 100% sure you start out with computers free of infections. I suggest buying a 64GB USB3.0 flash drive and putting all the files you wouldn't ever want to loose that are on your computer or phone onto it. I'd suggest manually transfer your files over individually instead of creating system images. I find it best to never store any personal files on the computer. If you're hacked they're gone or used against you. If you need to access a file plug in the flash drive, use whatever application on the computer to do whatever it is you need, and save it back to the flash drive. This is an easy step. For backups you'll want to have it in multiple places on multiple devices. If your flash drive dies with all your data on it you're bleeped. If you have two of them kept in a desk at the house and it burns down, your bleeped. I'd say keep two flash drives, one for perm backups and one to use regularly when you need to access a file. The third backup would be using a paid service so you have a backup out of the home. Don't attempt to register to any offsite backup services till after you're sure you have a computer that's infection free.
Go unplug your router/modem from the wall and on your personal computers gather all the files you need to keep and transfer them to the flash drive. Safely eject and unplug the flash drive. Plug it back in and look to be sure all the files are on there. Eject it and unplug it again. Do this for all the computers you own. Also at this time when the wifi is off put your phone in airplane mode and remove the SIMM card. Backup your phone contacts and personal files just as you did on the computers. You can probably plug your phone into the mac and do it that way. When you're done doing this put the flash drive away and you can put your phone back together and turn the wifi back on.
Next you have to be sure none of your devices are infected. First thing you should do is set your networking equipment back to factory settings. After you do this set them up again, on any computer it wont matter even if its an infected one. Be sure you update the networking equipments firmware to patch any security holes. Set your own admin username and password for it. People can guess default passwords. After you do this keep only the computer you setup the networking gear on the network as a precaution against other infected devices for the next step.
Now you're going to use the recovery function your Mac has. Google how to do this if unsure. You're going to nuke and reinstall a fresh install of your Mac's operating system. It will basically to this for you. It connects to Apple servers to find what OS you need and downloads it, than installs it. Afterwards you know your Mac isn't infected by a psychotic hacker. The first thing you should do after installing a fresh OS is go and login to your networking gear and change the passwords to new ones! Use strong passphrases. Now you'll know you changed the password for the admin account on the networking equipment as well as the password for your wifi on a infection-free computer so nobody could have the ability to steal that information.
You'r main computer and network so far would be safe. Any other computers you own need to be nuked and reinstalled as well. Because doing this on Mac or Windows doesn't require you to actually boot into the OS no psychotic hacker is going to be able to do anything. Nuke and reinstall the OS on every other computer you own. Be sure you aren't using the "admin" or "root" account on any computer. By default especially on windows your first account is an admin account that has full access to the system. If you get hacked on this any security kinda is useless but not totally. Make "personal, user" accounts. These if hacked would be less of an issue to the whole system as compared to it being an admin account. Lastly, nuke and reinstall your cell phone. Now you know your devices arent infected.
From your new infection free computer I suggest you Buy and download Antivirus and antimalware for windows computers. I'm not sure Mac is such an issue for this. Apple is pretty good ad protecting their OS. Still be sure its updated and ask Apple if you can get any protection for it. Change every password for any account you have for email, banks, this forum, facebook, etc. Use new passphrases for everything. Don't use anything you used before. First be sure you change your email password for accounts you used it to register on websites. You'll want to lock out any psycho hacker there first. Next change any account associated with that email. Be sure to get em all. Now you know on an infection free computer you changed all your passwords so nobody could so far know them.
So you're computers are secure, your accounts secure, what next? Stop doing stupid crap that'll get you infected. Don't torrent pirated software. Only install software you bought straight from the people who make it. Quit going on nastycore fetish websites. It's a bad habit. And you'll get infected with virtual STD's. Stop throwing away personal stuff. Shred your mail before throwing it out. If you go to the ATM opt out of getting a receipt. If thats not possible tear it up till you cant anymore and keep it till you shred it at home again before throwing away. How's anybody going to get any financial info on you if you don't make it possible?
If a website isn't HTTPS don't use it. If you go to a website and in the URL box there isn't a green lock icon your connection isn't secure, so bleep that website. Lastly put a god damn nannycam up at your work station. If some weird crap happens you can take it home and look at the recording and know who the psycho is.
Don't rule out the possibility that you're actually the asshat doing this to yourself. People don't just sleepwalk. People actually sleep text, sleep call, sleep work. The best part is they never remember it and might actually delete what they do so they never see it when awake. If you do have an issue where you don't recall doing things like writing on your own work bench at work the nannycam will prove it. Somebody screaming at you that they don't molest their family only happens if you accuse somebody yourself or somebody tells somebody that you say that. You're problem is because of an actual 19 year long stalker, you doing things in your sleep, or you having an issue with not recalling things you've done throughout the day.
If you find out its one person or a group of them get proof and put restraining orders on their psycho butts. Really 19 years is wayyyy to long for any issue like this. So either you do it to yourself or someone you know in person has been having a good laugh for 2 decades.