About a week ago, after sex, I felt very weak like I was going into shock. I was having low abdominal pain and then started bleeding for about three days. It was light. I'm on my period now but it is heavier than usual. I keep passing clots of tissue that are dark red and experiencing low abdominal, back pain, and headaches. After my weird sex experience I thought I was pregnant, but I waited to see if i got my period. Am I having a miscarriage instead of a regular period?