I'm paranoid that I have an STD? (I'm a virgin.)?

Get tested if you're paranoid about it. Usually you can't get STD's from drinking after someone else. That's not to say you can't catch other diseases though because there is bacteria from the other person and that may cause small infections but it's very unlikely you got an STD from sharing drinks. As for sharing towels and such, it was so long ago that you would have definitely seen symptoms by now. I would still go get tested though because stressing out about it can actually weaken your immune systerm. It's never a bad idea to get tested.