bad cramps

Lou

My period started 4 days ago and only lasted 2 days. now I am on cycle day 4 and I only had a bit of brown spotting but I am getting really bad period like cramps. It's getting worse over the evening and my lower back hurts a little too. has anyone had this? I did get a BFN the day before my period. This cycle all I took was bromocriptine and it was my first month on it.