You are going to need to get a new girlfriend.  

I just fucked the hell out of your current girl and made her understand what it is like to be with a real man.  I spent the past four hours pounding her hard. She is passed out in the other room with my cum dripping out of her stretched out twat. I don’t think she will ever let you near her pussy again. 

Why don’t you clean her pussy juices off of my thick cock?  If you do a good job getting my cock clean, I will reward you.  I will shove my big, thick cock into your tight little ass and carve out a cunt. You will get to feel the same pleasure that your girlfriend felt as I rammed my dick into her over and over.  The exquisite pain of having your hole stretched out to fit my meat. The true joy or servicing a real man, like the faggot you are. Once you have been cunted, you will be willing and able to take the cock’s of real men anytime and anyplace.

Maybe, you won’t need to get a new girlfriend after all.