You're 20.
If I had a son that age I'd tell them it's fine to masturbate. Two, three times a day. Sure.
I would suggest avoid watching porno movies, they're very unrealistic of what sex is about with someone you will eventually have a relationship with. Don't think your first time is going to be f*ing her from behind while pulling her hair and slapping her ass yelling, "who's your daddy."
Same goes for reading stories. 99% of them are unrealistic. Not every guy has a 9 inch dick, and not every girl is tight or 38 EEEs.
It's okay to look at porn. But keep it to pictures. You're young and curious and there is nothing wrong with having thoughts. Find a girl, get to know her. As you do so, feel free to after a date go home and masturbate thinking about her. Open up to her.
When you get a girlfriend, focus on her and not the internet porn. Channel your porn thoughts into loving and adoring her.