For some reason, I've been having period-like pains in my lower abdomen...This has never happened to me before.

I had unprotected sex a little while before my period, and got it on May 6th, and it ended on May 10th. My period is usually 6 days every month, and this time it was a day late, and it was less heavier. My periods have been crazy these past couple months. First it starts out around the 15th, then the 12th, then the 5th, and now the 6th.

It first started off as EXTREMELY light red, almost pink and barely noticeable. Then it got a little heavier, and towards the end, it was brown...I did pass a couple small clots...And a day or two after this months period was done, I had sharp period-like cramps in my lower abdomen. And today I had them again...I checked for any type of spotting or blood, but nothing. I'm on a good diet, I'm pretty healthy, and lately I've been taking prenatals to help my hair and nails grow.
Any help? %-)