Why cheat instead of just leaving?

Hi everyone.. I’ve never really posted on here I’m going thru it I’m getting sober and ended up getting really sick my kidneys and liver had shut down I was almost a goner. I had to stay in the hospital of course for some time. Fast forward to now I just found out he’s been talking to his high school sweetheart like kissing her and wanted to set up a visit where she’s at and blah blah blah. So I’m just fed up and done at this point I got a lot to focus on and keep from drowning. He won’t leave he’s been sitting in the garage for the last couple days he’s left us alone but this can’t work like this I want him to leave any advice?!?

Thank you all for reading and advice in advance.