Dad cheating

When I was 17 or 18 (not exactly sure tbh) I found out that my dad cheated on my mom. There was at least one confiremd incident, yet I believe he went out to strip clubs etc multiple times as well. I would like to also mention, that my dad is a very good person otherwise, he works hard to keep our family happy. I found out before my mom did but I kept my mouth shut because I really didn't know what to do, I have never told anyone about this. A few weeks later my dad confessed to my mom along with several things regarding his mental health (how he never got over is fathers death which happened at a very young age). I didn't hear the entire conversation but I overheard a lot. The went to couples therapy, as well as individual therapy (which he still in regarding his mental health) and worked out most of their issues I believe. Both of them and probably me have a lot of pressure in life due to my younger brother also being handicaped. At 19 (about a year ago) I left home to go to university and I only visit my family in my holidays because my school is far away, it wasn't easy but I've adapted. Anyways, I thought I had worked out the whole cheating thing and could somehow forgive and look past it.
When I arrived home for my break, sad news welcomed me as my Dog had died. It came out of the blue. As I was looking at old pictures of him on our family I pad the other day, which has my dads phone gallery synced, I found old pictures. Pictures of text messages, ones I hadn't seen before, about 10 years old, older than the first time I found the stuff on him cheating. I don't know how many times it happened in total, but I feel awful, I feel sick to my stomach and I don't know how to go from this. I am not suicidal or anything, I just feel like shit.
Sorry for the probably very confusing and badly written text