Erectile Dysfunction

Hey bro I know the feeling, and your right.. Thinking and worrying about it will just make matters worse.

I hope you girlfriend is understanding to situation. Its even more difficult if she becomes frustrated or upset. Sometimes it can make girls feel like there not good enough. Just reassure her about her body and sexuality and that may help you too.

Do you drink ?. If so try having a beer or any light alcoholic beverage with her before hand. This well relax you more than you realise, but don't have to much, you don't want the undesired effect.

After a few times of it all working out your confidence will be boosted and it should no longer be a problem.

P's: maintain a healthy diet, a poor diet can often contribute to a lack in performance. And keep your hands of it - abstain from masturbation and this should also help you get aroused.

Stop thinking about it. Have fun with her, do something that turns you on like eat her out, play with her whatever. But dont worry about yourself. Focus only on her pleasure and dont even bother with yourself. It may even take practise to break old habbits with confidance, but keep relaxing and get into the groove of making sex a relaxing fun thing to do. Make sure youre enjoying it man, I think thats key.
Find something and focus on it like her tits. Thats just my personal fav coz my girls got hotties!
Also, yea condoms kill the fun. But you just have to get that thing on quick, stroke it a bit and get it in there. What I do is open it up get it all out so I know which is the right way on, and then get with fore play. When were ready just forget that you dont like condoms! But bro I can almost promise that there's nothing wrong with you besides what's in your head. You have to shake the frustration.
I find that, the longer you mess around before you get right into the poking, the better your errection will be. Maybe its just me but probably not. Good luck bruuh

I wouldn't recommend drinking before you have sex. My husband has a difficult time staying hard when he's been drinking.

Keep off the drugs, away from the alcohol, and what not. It'll only make it worse. It's likely just nerves at your age (as much as you might not want to believe it).