My Fiancée and I Used To Physicallt Abuse Each Other

We are both women. Back towards the beginning of our relationship when we both had moved in together, we physically abused each other. It all started with a 3some gone wrong where I felt she was crossing boundaries. She hit me first and then I hit back and it all went downhill from there. I’d never hit anyone in my life, I only ever harmed myself. I later found out that my antidepressants would cause me to be uncontrollably angry if I missed even a day which is why I was so aggressive and mad. Not an excuse but a reason as to why I did what I did. I don’t know why she hit me. I finally changed my antidepressants and the physical abuse stopped. We can never tell anybody about this.