He has a GF. So what? If that's a big deal in your personal boundaries, then walk away until he is single. Work on yourself and be a great option for someone ELSE that might find their way into your mind and heart.
You indicate that you want to fix yourself? In what ways? What specifically do you want to "fix"?
Of these things that you want to fix, are any of them ALSO things that your X might have had issue with? Bonus points on those ones that you fix.
So, back to basics... beginner's mind...
If you could answer the following:
Is your X having a GF a boundary? ie. You will not pursue someone who is in a relationship.
