No... you cannot catch an STD in this way. They are called *sexually* transmitted diseases for a reason. You must have sex (anal, oral, vaginal) with someone to get them.
No it's your OCD, I would suggest you really talk to your Dr. to worry about this is really far out there. (just being honest) . NOTE for anyone else readint post response from Hensley258. FYI this needs to be said, when he talks about having unprotected sex, any kind of behavior like that after 1980, is called RUSSIAN ROULETTE PERIOD.
Yea, that's your OCD talking. Lets put things in prespective. Take me for example. In the last 22 years I have had un-protected sex with over 150 Women. I sit on public toilet seats and only wash my hands three times a day.
Guess what..... I am 100% disease free. Well, besides my cronic depression and anxiety dissorder, but that was not caused by any infection.
Our bodies have an amazing imune system that does a great job of destroying most any germ we come in contact with.
Granted my past sexual behaviour was a little risky, but this just goes to show you the odds of catching an STD from a toilet seat. In fact you would have better odds of winning a multi-state lottery while being struck by lightining than to get an STD from a toilet seat.
I understand that if you have OCD that what I said still doesn't make you worry any less, but trust me your fine.