Cramping right after period

I had unprotected sex on 7/24 my period was due on 7/25. It came on 7/26. It was it's normal flow (heavy) however I had massive blood clots like the 2-3inches long. Basically the size of a finger or earthworm. My period ended on 7/30 and on 7/31 I had brownish pasty spotting. I had a slight headache and cramping starting on 7/31. On 8/1 I had unprotected sex, prior to that I still had cramps and a slight headache. On 8/2 I woke up to a worse headache, the cramping got worse and I slept an additional 3 hrs after taking tylenol. I woke up to the same headache and cramps. On 8/3 the cramps worsened and the headache and on top of that I started have dizzy spells and I started feeling spasms in my abdomin and my temp was 97.7. I am still taking tylenol and nothing works. 8/4 I still have a headache and the pain got worse. I can tell you exactyly where my uterus is and when the pain hits hard I only feel the intensity on the left side. I still have dizzy spells and now nausea. Someone said that it could have been a miscarriage. I dont know what to think.