Period pains

When I was ovulating we had an accident while pulling out. I was a couple weeks late on my period so I took 3 pregnancy test and all were negative. I started my period and it was a very abnormal flow. It was thick and brown but it was only there when I wiped. That went on for 2-3 days but then my flow changed to heavy and it appeared to be normal. There were some pretty big clots but I didn't worry too much about them. But now I'm 12 days into this period and I was woken up this morning with terrible cramps in my left hip and pelvic area. My cycle is usually normal and only 5 days long. I have no idea what's wrong but something doesn't feel right. Please help!