Why Am I Bleeding After Foreplay?

Every time my boyfriend has fingered me, I have bled. Last night it happened again, but not only did I bleed, I started to get pains in my lower stomach. They are gone today, and only lasted last night, also I am no longer bleeding, and It wasn't much blood, mostly just spotting. My hymen is already broken, so I dont know why I keep bleeding. Also, the last time he fingered me, I actually saw my lower stomach move up and down. It was strange, it didn't hurt at all, but I never realized that before, and just wanted to know if it was normal. Please help.

Much appreciated.