At the time of sex my penis wont stay hard enough but when i watch porn or masterbate it stays very strong is it ed or what i am facing help me?

Situational: If you are able to attain an erections in certain situations (porn) but not in others (with a partner), then you probably have situational erectile dysfunction, meaning that there is likely nothing physiologically wrong but that there is something about sex with a partner that makes it more difficult for you to achieve a firm erection.

It's psychological.: It sounds like the cause of your erectile dysfunction is more psychological than physical. Perhaps, it would be good to seek couples therapy or counseling if you are in a committed relationship. Otherwise, you may be displaying some inhibitions during the act which go away when you have distanced yourself. Guilt or other emotions can interfere with your ability to enjoy yourself. Have safe sex.