About three weeks ago I had sex with my bf and since he was somewhat bigger I felt like I was gonna be on my period afterwords; I was bruised on my vagina, swollen, and crampy. After a couple of days all that went away it delayed my period a couple of days my period lasted a little longer, I wasn't too concerned until a couple days after my period ended I masturabated not externally and when I woke up in morning I had very dark brown and red blood discharge and it is going on for a day now. What could this be? Should I go to the doc?? Please help!