About time I make a change

I’ve been watching porn since I was 13,I’m 20 now.
I’ve been trying to quit for 4 years now, it’s been causing problems in my relationship and I need help. I’ve told my gf about it and she’s been helpful but I still find myself sneaking it in when she’s at work or sleeping. I feel like shit, I feel like I’m cheating. It’s to the point I’m having porn induced ed sometimes. Anything helps. Please