So I have this really strong fantasy about fucking my girlfriend in the ass while she pleasures herself with a dildo, but I don't really know how to bring the subject up. We've tried anal in the past and at first she didnt really like it but I think its grown on her because shes seemingly enjoyed it more and more when ive fingered her ass while fucking her, and shes let me stick my cock in there since (as long as we go slow she seems to really like it). Anyways, i dont want to do this with another man, just me and her (wouldn't want to share her). Any advice on how to broach the subject would be much appreciated....