Had Unprotected Sex, Ended Up With Brown Discharge, Frequent Urination, Dizziness And Abdominal Pain. Am I Pregnant?

I had an unprotected sex on first weekend of this month (Sept 1-3). Three days after, I had a brownish discharge . (Wednesday and Friday). It stopped during sat and sun. then i had brownish and sometimes pinkish discharge again Sept 10-15. it got heavier on the 16th and 17th but it was much much lighter than my usual period. Bleeding stopped on the 18th. My period usually lasts for 5-7 days. And I bleed pretty much heavy. Today, I have very light bleeding again. For the past days, I feel so tired all throughout the day, I have frequent urination (which is so unusual for me), my breasts are tender, I can’t stand travelling because I feel dizzy. Sometimes I have nausea , my lower back aches oftentimes, I feel heartburn , headaches. My lower abdomen hurts sometimes but I don’t usually experience this when I’m having my period. And I eat more than what I usually eat. Sometimes I had weird taste buds that the food I loved to eat tastes metallic or something. I had a hPT done twice already and the results are both negative. What could be happening to me?