What do you suggest if i am 42 years old and on most occasions i can get an erection but problem is sometime it don't last.?

Erectile dysfunction: First and foremost you need a complete history,including extensive family history, and complete physical . The problem you describe is common and usually can be improved or rectified. My other concern is that you are 42 y/o male and need to be screened for "possible" underlying vascular or coronary disease as ED can be an indicator for heart issues. Good luck and hope of some use.

PDE-5 inhibitor: Inability to get or keep an erection can be a physical or mental issue. First, go to your primary care doc and get tested for medical conditions that can affect erections and get screened for mental issues too. High fat meals and alcohol intake can affect erections so avoid them. Taking a PDE-5 inhibitor medication like Viagra (sildenafil) before sexual activity will help regardless the source of the problem.