Insecurities 😕

Fairly recently, I found out my bf (over 5yrs) had been with other women while we were together. We have a child together.. He says it wasn't anything that I had done wrong. Says he's never imagined living his life with anyone but me.😒 Doesnt want to lose me. 😒Apologizes, makes changes, but how do you know a person is sincere after so much deceit? It's impossible to babysit another "adult," i know. Just trying to find my footing again with all this. I feel drained right now.