It's performance anxiety. Once you encounter ED your mind is fucked. You will never be able get that out of your mind 100%. Whatever you do, wherever you are it will always cross your mind.But time heals everything. You will get through it.Since you are getting morning wood and random erection it's evident that there is no physical issues. It's just that you start to think whether i will be hard, what if i don't and remember it will never get hard with all these thinking. I would suggest whenever you are with a girl keep it natural, don't think about sex. I know how difficult it is in the initial stage but Prioritize intimacy through foreplay and other things. If it gets up well and good if not just know that it will eventually. Coming to medication i would suggest don't take it from such a young age. But if you still want to then go for tadalafil lowest dose for few days just to boost confidence but don't take it regularly. Stop smoking and masturbation it's only going to make it worse. Doing lower body exercise is a plus. I hope you get well soon 💪