i use to run 3 times a weeek 5k in 18 mins, then box after that, i've been diagnosed with A Fib. Dr's have told me to stop running and take it easy in the gym. I know it's very difficult i'm itching to get back. However when you train your heartbeat goes up. That can be a cause of triggering an episode of A fib. I guess it makes perfect sense. The only thing i've been advised to do is light weights and walk. Hope this helped.
The only person that can accurately answer that would be your heart doc......if you are feeling that the atrial fib is becoming progressive it sounds like some sort of aggressive treatment may be needed with intervention such as medications, etc. I wouldn't even attempt this w/out clearance from your doc and make absolutely sure that they are aware of the fact that the situ is getting a little worse so that they can take care of this.