Another CSA survivor here.
I talked to my BH about the abuse sometime after d-day. I had tis vague feeling of needing to process it even though I had refused to talk or think about it my entire life. Except for telling my mom after it happened and her telling me I was imagining things.
I can relate to the fear that talking about your CSA after your infidelity has come to light is making excuses for your A. I would encourage you to reject that voice in your head. You own your bad choices. Processing CSA is tough and painful don't let guilt over your A be an excuse to stuff the CSA back in the closet. Keep working on getting healthy one step at a time.