Problem maintenaing an erection during sex

Dear Ask The Doctor: When I have sex with my girlfriend I have an erection during foreplay but when i get ready to penetrate my erection gets flaccid and limp.I am 40 years old but i still get erections,what is my problem

Dear Erick: The symptoms you describe are not uncommon. In fact a significant number of men below the age of 40 years experience erectile difficulty. Fortunately, most erectile issues in young men are not due to any physical illness but are really psychologically related. Discuss the issue with your family physician. He/she may be able to isolate the specific issue affecting you and prescribe the appropriate treatment options that both you and your partner can participate in, to help overcome this problem.