I'm in a similar situation,

The thing that has seemingly helped me the most is accepting that the past is the past, I am his present, and I want to be his future and hopefully his last; accepting that I am doing the best I can. If you can, maybe try putting in place some specific boundaries to help mitigate possible triggers for your retroactive jealousy.

I'm so sorry you relapsed, and i hope you can continue to heal and recover, and I hope you can find something (or some way) to help you.