Period then flu

So I had my period October 30th until November 3rd, it was my first real period after stopping my birth control pill. A few days ago I started feeling nauseous as if I was getting a stomach flu, then last night I started having lots of diarrhea and same with today. I feel so sick. I’m pretty sure it’s just the stomach flu. (Me and my bf always use condoms and pull out, we even fill the condom with water after each time to check for holes and there’s never been any.)

Am I just over thinking ? I have really bad anxiety and being pregnant is my biggest fear rn.