I'm not a knee-jerk fan of therapy, and good therapists are really hard to find IMO, and I don't think therapists provide some magic bullet solution, but in your case I think having some good, hard, constructive, insightful conversations with a therapist about why the heck someone like you is so damn in love with someone like you H ... might help you sort out your feelings, and give you support for making the right decision.
You're lucky that you're young and do not have any kids involved. It gets hell of a lot harder when there are kids involved.
Me: 50, MLC/WW 45 Young kids Nov 2015: BD1 Apr 2016: BD2 Jan 2017: W filed Feb 2017: D final