Left back/flank/ovary area pain

Missy
I'm suppose to start my period today or tomorrow. I'm getting really bad pains in my left back/flank/ovary area. I never get back cramps with my period. I took a hpt a few days ago and it was bfn. I planned on waiting to see if I start my period to take another one. Any ideas of what that pain could be? Anyone else experience it?