My new girlfriend is really hot but i can't get a full erection! what can i do?

Well, first stop: Worry, may be adding to the problem. Look at your meds, Prozac (fluoxetine) or any of it's relatives may contribute. Consider getting testosterone checked, though likely not a problem. Consider some Cialis or other similar agent, do not want this to play on your brain and become a cycle where u are so worried about penis it doesn't work well. If u masturbate like 3x per day, throttle back a notch. Gd luc.