To be perfectly honest, this sounds like stress induced ED. It happens. And you are not alone. https://www.healthline.com/health/erectile-dysfunction-anxiety-stress#treatment Do they have counselors where you are at? I'd first, just to be safe, get a physical. I would guess the findings will be that everything is normal. AT that time, mention the issues sexually with your girlfriend and ask about counselors that they can recommend. This can be very effective at moving through anxiety. They may teach you techniques to not overthink and talk yourself into being stressed when you meet with your girlfriend.