Kinda embarrassed to ask this but is there something wrong with me? /u/UsefulDig2976 Sex

I (19M) have had sex like 4 times but idk if I want to do it again. When I kiss my gf before sex I get hard, but when I take my clothes off it goes away and becomes difficult to get it up again and to make it worst I cum too fast like 3-4 minutes into penetration, all of this makes uncomfortable because I can’t have sex properly, before start dating my gf I didn’t had sex before I didn’t use to masturbate a lot (1-2 times a week). So I don’t think masturbation is the problem. Obviously want to have sex and I’m very attracted to my gf, so don’t know if there’s something wrong with or all of this things will eventually disappear with time, but at the moment I don’t to have sex again because of this things that happen to me. For sure is my problem, but idk if someone has some kind of advise for me. Sorry for my bad English, I’m not a native speaker. Thanks for your help.

I (19M) have had sex like 4 times but idk if I want to do it again. When I kiss my gf before sex I get hard, but when I take my clothes off it goes away and becomes difficult to get it up again and to make it worst I cum too fast like 3-4 minutes into penetration, all of this makes uncomfortable because I can’t have sex properly, before start dating my gf I didn’t had sex before I didn’t use to masturbate a lot (1-2 times a week). So I don’t think masturbation is the problem. Obviously want to have sex and I’m very attracted to my gf, so don’t know if there’s something wrong with or all of this things will eventually disappear with time, but at the moment I don’t to have sex again because of this things that happen to me. For sure is my problem, but idk if someone has some kind of advise for me. Sorry for my bad English, I’m not a native speaker. Thanks for your help.