I always finish sex sooner than my partner. How can I last longer?

Many men occasionally ejaculate sooner during sexual intercourse than they or their partner would like. As long as it happens infrequently, it's probably not cause for concern. However, if you regularly ejaculate sooner than you and your partner wish — such as before intercourse begins or shortly afterward — you may have a condition known as premature ejaculation. Premature ejaculation is a common sexual disorder. Estimates vary, but some experts think it affects as many as one out of three men. Even though it's a common problem that can be treated, many men feel embarrassed to talk to their doctors about it or seek treatment.
Once thought to be purely psychological, experts now know that biological factors also play an important role in premature ejaculation. In some men, premature ejaculation is related to erectile dysfunction. You don't have to live with premature ejaculation — treatments including medications, psychological counseling and learning sexual techniques to delay ejaculation can improve sex for you and your partner. For many men, a combination of treatments works best.
There's no medical standard for how long it should take a man to ejaculate. The primary sign of premature ejaculation is ejaculation that occurs before both partners wish in the majority of sexual encounters, causing concern or distress. The problem may occur in all sexual situations, including during masturbation — or it may only occur during sexual encounters with another person.
Impotence. You may be at increased risk of premature ejaculation if you occasionally or consistently have trouble getting or maintaining an erection. Fear of losing your erection may cause you to rush through sexual encounters. As many as one in three men with premature ejaculation also have trouble maintaining an erection.
Health problems. If you have a medical concern that causes you to feel anxious during sex, such as a heart problem, you may have an increased likelihood of hurrying to ejaculate.

Stress. Emotional or mental strain in any area of your life can play a role in premature ejaculation, often limiting your ability to relax and focus during sexual encounters.
Certain medications. Rarely, drugs that influence the action of chemical messengers in the brain (psychotropics) may cause premature ejaculation.