Hi Hisbiscus,
Your stoma was just a convenient excuse for him to cheat on you. If you didn't have a stoma, he'd find some other excuse to have his cake and eat it too. Trust your woman's intuition on this one. If you suspected that he was having an affair with her, he most certainly was. My first husband of 18 years also left me when I had health issues, and I knew exactly who he'd been with all those nights that he would wander in at 2 or 3 in the morning. Just like you, it was the betrayal (with the family "friend") that hurt the most.
But look at you now! Without that miserable, emotionally abusive dead weight holding you back, there is no limit to the heights you can soar! Sure, it's going to take some time to get your groove back, but you will. It's like being freed from captivity - bewildering and exciting at the same time.
Time will work wonders here. Now that you're no longer under his influence, you'll start to realize that every nasty thing he told you about yourself was nothing more than a pack of lies. I hope you DID let the door hit him in the ass on his way out. Hard.