Can it be food poisoning/ fatigue or pregnant?

Hello ladies!

So I’m kinda overthinking things right now. I ate something bad yesterday that’s causing nausea and my whole lower back pain. I also work from home so I sit 8 hours and sometimes I can’t get up. I’m paranoid that I might have to test. But I bled like a period just a few days up to 5, it was dark red and brown color blood to the point my pads were full of blood. I’m assuming that was my period???

Also context I am on birth control pill, me and my fiancé had sex last week and there was one time that I took my pill a few hours late. Every day I take it on time. I’m just paranoid thinking if it’s just fatigue from sitting in one place all day barely eating anything or the food I ate yesterday. My boobs don’t feel sore at all.

So if you ladies can give me some advice about this I’m gladly happy to listen!