Why am I like this?? Anxiety over sex help!!!

Okay so, I had protected sex four months ago for the first time. I know I’m not pregnant because:

I’ve gotten my regular periods every month since. Same heaviness (except this past month bc I start the pill) and same length of 7 days, right on time for each (really a day early each but I still think that’s one time)

I took a preg test 4.5 weeks after having sex and then 5.5 weeks after having sex and they were very clear neg. I could not see a faint line or anything.

I went for a pelvic and transvaginal ultrasound for heavy period and if I were pregnant I would have been 11.5 weeks by then. He said the results showed fluid in the pelvic region and I ask if it was in the uterus (expressing concern if it was the sac that would be present in early pregnancy although I know by 11 weeks you would actually see a fetus). He said I was fine and that this fluid is something else.

But I cannot stop thinking about if I was pregnant and somehow missed it/ did a test wrong. Like it’s obsessive and idk what’s wrong with me.

The two thoughts that keep making me worried:

I’ve had heartburn almost everyday and my mom said when she was pregnant with me, she had heartburn everyday. This scared me so bad. I’ve had heartburn before but not everyday like this since I came back home in April.

I was also looking at different ultrasounds techniques and my doc requested a non-ob ultrasound, obvi because I didn’t have any indication of pregnancy, so now my anxiety is making me think, what if they missed it because they weren’t actively looking for a fetus??

Please tell me I’m crazy. It’s mainly the heart burn making me make myself miserable through this anxious thinking. Why am I like this? My mom always told me that I would get pregnant if I ever had sex and my life would be thrown off - so maybe I feel guilty for having sex? I don’t want to feel like this every time but I also do want to have sex with my boyfriend. Why am I obsessing over this???