I keep having these thoughts that are tearing me apart, 1.st What if somehow these people contact my family, what if they contact my employers, what if they contact my friends? I know its unlikely, but knowing it could happen terrifies me. Then I think of what I should do to prevent this which leads to more anxiety
Well, think about how this is tearing you apart, and then think about the fact that, assuming you ever do decide to tell your parents, they will only be mad at you for a while, maybe force you to see a psychotherapist, and eventually forgive you IF you choose to cooperate with them and try your best to stay employed and never give them any hardship again. At what point would dealing with their wrath be easier than being alone trying to deal with this?
However, I am not about to join the calls for you to come out to your mom and dad, just yet. It is just very embarrassing to have to ask them for help because you know they never let you forget it for as long as they live. You know that they will always be in your life, and you don't really want to have them drag this out every time they want to get something out of you. I get that. You are not crazy to not want to deal with that if you do not have to. It would be one thing if you were a full-time zoophile and that fact were not about to stop being a part of your life, but this was a one-off incident that you were pressured into.
At this point, the wise thing to do is to stay focused on the people that are not really jumping in to abuse you over this, surround yourself with them, and avoid interacting with haters at all. Don't argue with them. Don't plead with them. Like I said, they are bad weather: they might hurt you, but so can any force of nature. COVID-19 can hurt you: you take precautions against COVID-19 by applying a lot of hand-sanitizer, I would assume. You might be scared of COVID-19 and should be because it really is dangerous, but you don't cry yourself to sleep about it, I hope. Toxic people in your social life can also hurt you, but what you do is take soundly advised precautions to protect yourself. The best thing to do is cut them off. Block them, block them, and block them some more.
Stay close to people that make you feel safe, especially ones that understand your situation and understand why you feel scared. Put those kinds of people in your social life. Talk to them about anything. Talk to them about food. Talk to them about the weather. Talk to them about how they are staying safe during the COVID-19 pandemic. Talk to them about movies, your favorite shows, anything, ANYTHING, to keep them in your life.
Be smart about protecting yourself. It's just like COVID-19: you play smart, and you play safe. It WILL blow over.
However, if your situation gets to a point where your existential safety or your freedom might be at risk, that is the time to go straight to your parents. That is what normal parents do: they do anything they have to in order to protect their offspring. And hold it over their heads for the rest of their lives, yes, but when it comes to your life or your freedom, those things are more important.
Stay safe, and stay smart.
And by the way, if you were underage, at the time that that video was shot, A) then the people that are distributing that video are guilty of distrubuting child pornography, and B) you were a minor at the time and cannot possibly be charged as an adult. They can be charged as adults for a serious crime, and you cannot. A prosecutor could not possibly prove in court that it was you unless they looked at the metadata on it, which would also reveal that you were not legally an adult at the time. That popular girl is disseminating kiddie porn and is a criminal. Do not warn her. Do not alert her. Keep that card up your sleeve for when or if you need it. Never play fair with vicious people. Never give them warning. The less that vicious people know, the better. I think that knowing you have that card up your sleeve if you ever had to play it might make you feel better.