Is this the only thing that causes you to think irrationally? Did you actually do anything that was actually risky or is this a phobia? Are you chronically anxious about lots of things? The answer to these questions will go a long way to helping you find a way out. If this is the only thing that does this to you, it's probably a problem you're having with sex. Lots of people have problems with sex. If it's just the one thing, and it drives you this nuts, see a therapist and talk it out and figure out why this aspect of your life is so different than all the other things in your life that can lead to illness and harm. Do you worry about driving? Much more dangerous than sex. Do you worry about pollution? Much more dangerous than sex. Do you take proper precautions when you have sex or are you cliff diving? This kind of thing can be worked on. If you're just a chronically anxious person who worries and obsesses over everything or lots of things, that's a different therapy problem and if it's severely disrupting your life might lead to medication. Which is it?
I'm here, I'm with you, I'm in the same circle of worries. And I AM in the window period and I still need to wait for 3 more weeks to go get tested.
I just want you to know that you are not alone and, PLEASE, but PLEASE try to relax. It's not easy, I know. But, still... Life happens. We can't do much about our future, I mean... We can't easily control everything, right? If it was so easy to do it, than everyone would live a 100% happy life, without even one little problem.
So... Try to relax: meditate, take deep breaths, listen to some relax-music, close your eyes, try to calm down even for a second, then for a minute, and so on, and so on... I repeat: I know this ain't easy, but we MUST keep trying. Second by second, minute by minute, day by day...