Advice please?

Leanna

Soooo I started my period Monday but it was brown. This is Common but this time I'm have a sudden pain in my abdominal area. It's not like a cramp but it's continue. If I don't walk it hurts and it causes me not to eat. I'm on birth control (pill) and this is the first time this has ever happen the 3 years of being on birth control. Last time this pain has happen was when I was having an ovarian cyst erupt. Help?