I'm just now reading your posts, and I appreciate your openness and honesty. There's nothing to be ashamed of, as it takes courage to acknowledge a problem, and this is a safe space for which you can do so.
A lot of my posts and advice have a theme - practical strategies to help you push through. The issue with group classes and going to the gym (etc) as an escape from PMO is that they only occur at certain times. Now, I literally go to the gym everyday, so I'm not saying I'm against the gym. But here is the reality: it probably doesn't take longer than 1 minute for you to regress at any point. Relatively quickly you can open up your computer to whatever videos you find most fulfilling, whip it out, and start masturbating. 60 seconds. Which means out of the day, if you are awake for 16 hours X 60 minutes/hour = 960.
In other words, there are 960 vulnerabilities for you to relapse every day. So sure, a hobby or two can take care of 120 or so of those minutes, but what about the rest? I think the solution is the mindset you have to be in. I have found that planning out my entire day is very beneficial. I always know what task I should be working on, or person I should be talking to. And if something interrupts me while I am performing a task, that's fine, because my mind remains ENGAGED. I think the quickest way to relapse is to find yourself bored.
Keep it up, I look forward to hearing more about your progress.