I dont know if its the right place to ask. i lose my erection when im about to have sex with my partner, it starts off alright and then gone. why?

While always causing: distress, erectile dysfunction (ED) can happen at any age. There are many physical causes of ED--heart disease, diabetes, medications, drug/alcohol use, etc--but in a young man such as yourself psychological factors are often at play: stress, depression, relationship issues. Perhaps ED is not a problem when masturbating? (this is common) Your doctor sees this problem daily. Pursue cause/Rx

This may help: This happens to most couples from time to time. I'm going to assume that you're getting good, hard erections during foreplay and when you are enjoying your body by yourself. Rather than focus on the hydraulics, switch to using the rest of your body -- hands, mouth, whatever's right -- to keep pleasuring her. Generally, explore as a couple the many possibilities that your love provides.