Ok so first off I am rather new to sex and everything. Me and my gf have had sex about 5 times now and we were both virgins before that. The first time we had sex was kinda unexpected at least for me anyway and she just kinda stuck it in and we went at it. Well I had no problem ejaculating that first time but ever since then I haven’t been able to. We only go at it for about an hour as she gets really tired and sore after that but I don’t get why I cant ejaculate in that amount of time. I have no problems when I’m alone and masturbate but I cant seem to get off during sex anymore. I’m currently 19 and have been masturbating since I was 13 but I don’t do it the normal way. I only use three fingers, thumb on top and two on bottom and go at a rather fast pace. Could that be my problem? I’m kinda lost I know I get her off several times but I can’t seem to do the same.