This is not normal

So I have had unprotected sex last month.. anyways everything was fine, I had my period two weeks ago and then lastnight I was very nauseous and I had random and very tiny spotting.anyways . I could barely sleep I thought I was gonna throw up and I woke up feeling like that also.. I went to the restroom and peed then a TON of watery ( no clots) but very very dark brown blood

Why is this happening? I already had my period.

Why is it making me feel so sick