Compusive Worrying

This may not be the right place but I am new here and I think it ties in with anxiety pretty well.

For whatever reason, probably ever since I was 17 or 18 I have worried and freaked out over certain things, even when worrying isn't logical. For example, even though I always practiced safe sex with a girlfriend I had around age 18 about a week or so before every one of her periods I would be losing sleep thinking she might be pregnant. It annoyed her and made no sense at all.

Fast foreword to recently, I had another girlfriend that lied about a few things and long story short there was a small possibility of pregnancy based on what we did but it was incredibly small. Now I worried incessantly for the weeks leading up to her period but even after she told me she wasn't pregnant I couldn't shake it. I began imagining that she was lying about that also and came up with all these theories as to why. I even stalked her social media and what not (we were broken up at the time) because I was so certain she would start to look pregnant.

All I ever found was a lot of pictures of her going out getting drunk and having fun at concerts etc. Even then I began thinking maybe she was just pretending to drink to trick me, or she just didn't care about drinking during pregnancy.

fast forward to now, its been about 27 weeks since she would have gotten pregnant and she still looks like the day she did when I left her. Yet I found myself zooming in on her pics and almost convincing myself her belly was bigger or something.

Once I finally snapped out of this (sometimes I still have random anxiety about it) I instantly started convincing myself I have HIV. I invested probably 30 hours researching about it after work. I only quelled that anxiety when I actually spent a night calculating the odds which were insanely low.

What do you think is causing this? I appear to be a normal person to everyone who knows me. Only thing I can think is I've only really fallen in love with two different girls in my life and both lied to me in very bad ways (one was a cheater, the last I referred to "forgot" to get her birth control shot).

Is there anything I can do to control this. Keep in mind I'm a 22 year old dude. I don't explore my emotions are talk about this stuff with people often.