All in my head?

Hi

I was hoping this problem would go away but it hasn't, so I'm reaching out for help.

I'm a 23-year old virgin. I have had some sexual experiences (in fact, pretty much everything apart from penetration). The first time me and my first girlfriend tried having sex (I was 18 yrs old), I struggled to become fully erect and I think we tried to rush through the foreplay and that's why. But ever since, I've had this anxiety that the problem will happen every time. I've only really been with a couple of girls since, and one of them very recently - and lo and behold it happened again.

I can get erections perfectly well whilst watching porn or masturbating, and even during a bit of foreplay with this girl. But as soon as she mentioned 'sex', I lost it completely and I couldn't think of anything else other than my erection.

I don't think I have any physical issues. I'm a perfectly healthy male who eats fairly well and exercises regularly. And, as I've mentioned, I can get erections at other times.

I'm wondering whether this is a purely psychological issue and how I can get over it? I'm really concerned that this is never going to happen for me and I'm worried that I won't be able to develop relationships because of it. Please help, as it is completely taking over my life right now