I am in too much confusion, I think either I gonna mad or really need a psychiatrist. Sir my problem is that I have a sexual fantasy that includes the threesome sex . Whenever I imagine having sex with my gf with including a other male guy I turns on.I asked for this to my girlfriend initially she said no directly but now she is ready for the same, we also arranged a guy wo will join us, ultimately this guy is her colleague and he is also ready for the same, when everything done, then this time I am stepping back from this fantasy but when again I thought of it it turns me on badly. . Please help me whats wrong with me?Should I go for it?