Yes sounds like your on the verg of ED, due to porn enduced ED,ie to much porn and masterbating to it, so you now dont get turned on by your g/f, so yopu just need to stay off sex and masterbating for the next 8 weeks, and let your body reboot, you can read all about this by googling porn induced ED.
Good Luck
Just give it time and your body will heal itself, so just tell your g/f the truth and tell no sex for the next 8 weeks as you have a small problem.