I have always had this problem as well. According to the experts it can be a mental or physical problem. If you can masterbate in private and get off in 1-2 minutes and you have an orgasm (some guys can ejaculate without an orgasm) the problem is probably mostly mental and can probably be corrected. A lot of that has to do with a guy's head. If the problem also occurs during masterbation by yourself, it may be physical and there are a host of reasons. Chemical imbalances in the brain, damaged nerve path bicycle injuries are a common nerve injury, back or spinal injuries, smoking and alcohol and some other recreation drugs can cause problems, mental health drugs, diabetus, lots of young guys with type 1 have this problem and it is also common in type 2 diabetics, blood pressure meds, many others as well some correctable, some not. I have some that are not. A spinal problem, depression, diabetus, and bp med.
I found a book that helped me a lot:
Male Problems By: Dr. Bernie Ziberguild. I am not sure it is still in print but he is a psychiatrist who treats male sexual problems. If you get the book and and find out the negative things you are doing to your sex life it may help you with the exercises he has there for you to do. However, if you have a physical problem try out something else I found to be of help. A device a that you can find at sex shops or
Aneros Prostate Massage Massager Male Sex Toy, I am not advertising it may not even appeal to some of you straight, don't touch my asshole guys. It is however approved by the FDA for the treatment of several sexual disorders and has some added benifits beside. I have to tell you I have been using one for two years and I have never had the BIG "O" they talk about on the Aneros site but it has tremendiously helped me to orgasm and to enjoy the orgasm.
Often young guys will find this problem is because they are so uptight about sex and aren't sure what they want or are so nervous during encounters. The book has some really good exercises for that.