What Causes Missed Periods, Back Pain, Swelling And Migraines?

I've been having trouble with my period, and I missed 3 months. The other day I started, I think, but it was very little and it was blackish and only lasted a day. I also have extreme back pain located more toward the left of my back and top of my bum, it feels kinda swollen as well, along with sever migraines. What could this be? Should I see a doctor in person?