I have a same problem, my husband went to sauna (indecent I think) last year, I was very angry and disappointed. He swore to me and he promised me that he won't do that again, also, as I considered of my daughter, she was only 4 months, therefore, I forgave him and I told myself that was the last chance for him.
Unfortunately, he did go again last week, he breached of my trust. Of course, he denied going there...but I am not a fool.
No more believe of what they said and what they swore.
Anyhow, don't make such decision before serious thought, I meant divorce. Forgive him if you really can...because a single parent family affects the growth of child. That's what I concern, otherwise, I must leave him.
Yes, if you really can do that..forgive him, I know it is a difficult time for you at this moment, but, how time files, you must feel better when time pass by.