Lost my wife of 7 years with 2 kids, having trouble co-parenting because I didn't want things to end?

I was a heroin addict got together in 2017, ended up getting pregnant and stopping my addiction and was clean for 5 years but a year ago I relapse because of pain ended up in a coma for 30 days. Getting married in 2020 and having another kid, we switched focus off us and I believe that was our downfall. My 30 day coma gave her some type of PTSD. going to marriage counseling seem to help in March and April but then we bought a place to fix up down south close to her family because our current place was reminding her of the month that she thought I was dead, and we were supposed to resume therapy after, however someone that she said was just friend with she ended up leaving me for after just a week after completing the new house. But while we were working on it we were talking about things about the place and nesting and I thought that we were generally going to work things out.

Anyways I just saw them kissing and cuddling in front of the sink of the place we completely remodeled together, while I was trying to video chat my kids and I don't know what to do. This new guy makes a good amount of money but I feel like he got in between our failing marriage and pushed the insecurities of my addiction to my exwife and was forced to divorce. Even temporarily had a protection order against abuse of rape that is completely false put against me to help force the papers.

I lost full custody of my kids with just visitation rights but don't have to pay any child support.

I really just want my family to be together still, what do you think of the situation and what should I do?

Updates
7 mo
I did clean up and I got married, I had one slip up, and still lasted another year after that , while she developed feelings for somebody else... I don't know why she did this now I'm grieving alone, Don't even want anybody else when she has someone else
Lost my wife of 7 years with 2 kids, having trouble co-parenting because I didn't want things to end?
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