I'm so sorry you relapsed Obladi.
If I am understanding it correctly, it happened when therapy reopened old wounds?
The closet I have come to relapsing was in a very similar situation. I was forced to attend group therapy, it was torture. It triggered my ptsd and made all my past traumas raw and unmanageable. After the sessions all I could think of was to drink to alleviate the feelings. Luckily I didn't succumb but I did have to leave therapy and accept, for me, it is not healthy.
My past does bother me but it is better left there. Sharing it is just to painful and definitely not compulsory to recovery. What works for some doesn't work for others.
Wishing you the best.