During sex with my girlfriend I reach to orgasm late. But when I masturbate I got very excited and reach orgasm very quickly. However I masturbate by imagining doing sex with my gf. I got intimate 2 times with my girlfriend but I did not involved in intercourse, it was only some kind of foreplay. During this foreplay I reached orgasm when I started imagine some intimate scene with my gf even though I am already doing same thing practically but I don't know why I had to imagine to reach orgasm when I am doing same thing practically? Is it due to not doing intercourse or anything?