The cause of premature ejaculation is usually not known. It is a combination of hyperactive nerves in both the penis and the brain combined with psychological factors. There have also been certain brain neurotransmitters that have been implicated in premature ejaculation. For the most part, the cause of premature ejaculation in an individual is never determined. Most men "grow out of it" at some point and find that they don't ejaculate nearly as quickly as they used to.
Premature ejaculation can be very stressful on you, especially if you think it displeases your partner. Thus, I do think that you should see a doctor. The best type of doctor for you to see initially is a primary care physician
or internal medicine doctor
). He or she can discuss this issue, any other symptoms you may be having, and perform a physical exam. If no obvious cause of the problem is found, then your doctor can start you on treatment. I usually start my patients on a medication from the SSRI class (selective serotonin reuptake inhibitor). This is a medication normally used for depression and anxiety. It has the useful side effect of delaying orgasm which makes it a very good drug for premature ejaculation. Good luck.