Ok so i've been sexually active for about 5 years now. I have had 8 different partners in those years, some long term situations, other one or two time occurences. Sex is really enjoyable for me and my partner from my experiences but there is a nagging problem that has continued to haunt me and to an extent my partners for the entirety of my sexual activeness. Some guys have problems with pre-mature ejaculations and the likes but I seem to have the opposite problem...I can not come to climax through sex. Not once, not ever have I climaxed during sex. It comes to the point where we have sex for so long that the girl is too sore to continue most of the time. At the beginning it was great because I thought i was a machine "sweet, i can do this forever!" i thought. But as you can guess, most people would want to climax during sex with someone they care about. Furthermore, not climaxing may bring an element of doubt into my partner's head and make her think "am I not turning him on enough?". This is fully not the case, but I have no answers for my partners as to why I can't. A night will usually start with some foreplay and then sex for a ridiculous time until the girl is sore, and then it could take up to about 10 minutes of oral sex to get me off. I do not want to continue like this and me and my current girlfriend are trying to "fix" me. Should I see a doctor? Does anyone else have problems like this? Thanks.