Relapse and Breaking Up

I've been dating a girl for about 7 months now, and during the last 2 or 3 months I had a pretty good streak going of no PMO - there was a stressful time for me and I relapsed, and have had a hard time getting back on the horse since. It is around this same time that I have been questioning my relationship with my girlfriend. There have been some red flags throughout the relationship that I either overlooked or hoped would change in time, but now these things seem to be coming to a head and I can't discern whether it is my fault in a state of weakness that I am wanting to leave the relationship, or if now I'm seeing clearly that this relationship isn't sustainable.

The changes that are taking place now:
- I'm about to graduate college. (that in itself is a big one, and something that my girlfriend does not understand as she still has 2 more years of college left)
- I've relapsed on PMO 5 or 6 times in the last two weeks, ending a 56-day streak.

TL;DR: How do I decide whether or not to stay in the relationship and work through this hard, turbulent time, or leave? How does my relapsing with PMO affect the way I view my relationship? I'm very confused.