Period talk

hey ladies, I need some answers . I take birth control and never miss my pill, on the 9th of February I had sex during ovulation, my boyfriend didn’t cum in me but he precums a lot. on the 1st of March I was due for my period but didn’t get it, around 5 days late I took a pregnancy test that came out negative. Today marks 7 days since I’ve been late, but today , what I think was my period showed up in my panties. It was the size of about a quarter but it was a very dark brown. I put a tampon in and it turned more darker and red with some blood clots. I just went to the bathroom to pee again, nothing show up on the pad I put in a couple hours ago and no blood when I wiped. Wtf is going on?