i also find getting an erection with my wife difficult but to do that easily with a girl friend. what should l do l love my wife dearly.
I'd suggest dumping the girlfriend. How can your wife compete with that? The girlfriend has no responsibilities in the relationship. She does not have to help pay the bills, keep the house, raise your kids (if you have any), or anything else.
One has all the responsibility and the other has all the fun.