Curious ... Anybody experience this?

So I use 3 apps to track my period. Between three of them, my period is supposed to start between Thursday, today, and Saturday. Wednesday I found some magenta like brown blood in my underwear then nothing when I wiped. Last night, I saw small drops, not large drops, or blood when I sat down to pee. Then I wiped and it was that same type of blood just more of it. So I put in a regular tampon for the night. Woke up today, and it was like half way filled with brown and dark red blood. But I was still dripping those small drops when I just sat for a minute and peed.

Usually my period comes heavy and fast, it always has since I started my period at 10. So this is weird. Yes, there is a chance that I could be pregnant. My fertile window was the week of June 15th. We had sex on 17th and 19th unprotected with finishing in me. I have been nauseous for about a week and a half, lightheaded, tired even though I do stay on my feet at work, and lower back is hurting. I have dull cramps on one side at a time but was more on left starting out. Now it’s no cramps but my back is the main thing. It’s also been hard for me to poop and having headaches that last even after I eat. I have night sweats which I haven’t had in a while so my body is warmer. My bf says my nipples are darker and “flat” anymore meaning the nipple part stays poked out. I also noticed more white bumps when I squeeze and it’s more sensitive too, most of the time.

I took tow pregnancy test on Monday and Wednesday morning, both negative and before my period due date. And I haven’t taken anything since because I started bleeding...

What should I do?