All the other posters responses are very good and I'm sure very true where alcoholics are concerned...
I have no experience with an A, BUT I do have similar experiences to you...
I have always been a "busy" type of person... I have activities going on most nights of the week on top of my regular job. I have never been happy to just sit at home and watch tv. WELL, one of my xbf's was the exact opposite of me. He LOVED sitting at home with nothing to do and no hobbies/interests. No matter how much I would beg him to go out and socialize with me and our friends he simply refused. Finally I couldn't take it and I broke up with him. Literally 2 weeks later I found out from "our" friends that he was always out with them and doing stuff. Socializing like nobody's business... I just thought "Huh... why couldn't he do that for the years that I spent with him???"
With another recent xbf (that I had been dating for 6 years) I ALWAYS wanted to do physical activities with him, like hiking or swimming or bike riding, or anything active really. He always said no, he was out of shape, he was in pain, he was too busy. AFTER I broke up with him for a myriad of reasons; he IMMEDIATELY started doing physical activities to try to get in shape... he started going to the gym, started hiking mountains, started jogging! I could't believe it... especially that the same sort of thing was happening TWICE to me!
I don't know if either of them were dating anyone else when they suddenly started doing all the things I had begged them to do, although I don't think so. I am certain my recent xbf is still single even though we have been broken up well over a year.
So I do feel for you... it hurts to see them make the effort to do these things for SOMEONE ELSE when you're the one that put up with them and encouraged them for so long...
I try to look at it and think "Good for them... even if they didn't want to do these things with me, at least they're doing them now!". I am always the one that has broken up with them so the least I can do is wish them well...
Sorry I know this doesn't help your situation, so just listen to the other posters, lol!
Hugs to you and stay strong!
T