Can't get hard or stay hard at 18

Erection problems at 18?! Ok so this is my story also know as the worst thing ever ): anyway here's the story, so about 5 months ago I could get an erection whenever I wanted to, I've been masturbating since about 16 and about 2-3 times a day if I felt in the mood. But then I got a girlfriend about 4 months ago and things have changed, we were dating and I would still masturbate and everything was good. Then one night she gave me head for the first time, I felt my penis wasn't as hard as usual and just played it off thinking it was all in my mind. Then about 3 months ago we were going to have sex for the first time at her house and my penis just wouldn't get hard, I felt so shamed and like a loser. She said it's ok and we can do it again another time. I said ok and went home, I then thought I should masturbate to see if I was just nervous around her. I couldn't seem to get my penis past maybe 50% hard. I have now cut off masturbation completely hoping my erection would return, it hasn't ): Now it's been a full 5 months since the first incident, some positive things are when I'm with my girlfriend sometimes I get hard for a while but lose it after about 5-10 minutes of foreplay, and sometimes I get some pre cum (which doesn't seem good because I didn't even get close to cumming). Also some time at night I wake up with a strong erection but it goes away once I realize I have one because all I do is think it's going to do is just go limp. Some mornings as well I wake up hard or semi hard. I really don't know what's going on with me, I'm too scared to tell my parents I need to see an urologist, and I'm also very healthy, I play basketball, I had a perfect physical And my blood pressure is fine. This is the most embarrassing thing that's ever happened in my life and it has completely taken over my thoughts. It's all I think about now and it might just be making things worse, I hope someone knows what's wrong with me, any and all advice is appreciated. I've been contemplating suicide lately, If I can't satisfy the girl I love, and I can't raise a family what's the point of dealing with this forever? I don't want to lose this girl over this, please someone help me!!!!!! )': I can't do anything to get fully erect, it comes randomly for about 5 minutes and then I'll think I'm ok again, so I go to masturbate just to see if I can get it all the way up and I just can't!!!!