I have a new girlfriend who is a very sexy, beautiful woman. I've tried having an erection on my own, which I don't always have the best of luck with either. I don't understand what's happening because I thought these years were supposed to be my peak ones sexually. But you know, they're also stressful. You're wondering if you're going to measure up, what she'll think of you in the bedroom, if you can perform as well as the next guy.
Most men have trouble with their erections periodically throughout their lives.
But you're still human, and those hormones are all mixed up with feelings and emotions, some of which, in your case, include stress and fear. Go easy on yourself. Instead of putting pressure on yourself to get erect and perform, spend your time trying to please your new girlfriend. Explore and experiment. See what turns her on.