I am a healthy 19 year old male, and I workout and run very often. However, i struggle to last longer during sex but last way longer during masturbation. My first round is always very short (20 seconds) in both cases, but my second round is usually like 10 minutes during masturbation.. However this doesnt happen during sex with my gf tho. I just cant get it hard enuf for penetration during sex. This is really making it hard to enjoy sex… what could the cause be? Is it porn addiction? We are long distance relationship, so when i was away, i used to masturbate around 4-5 times a week. Or is it just some other problem? How do i fix it?