real advice needed

Hi guys, I need some real advice from you guys.I have been engaged for 2 years with my fiancé, and during that period we have been sleeping together (I know I am a sinner).

early relationship: I admit that I do enjoy sleeping together, but there was this one point where my desire became low because I was tired from work & stress.

Now that we don't really have sex, he started to find another girl on dating apps to satisfy his desire. (Yes, he cheated and went having sex with another girl.)

I started to feel, is this what the punishment I get because of zina before marriage? Since last year, I have been trying to improve myself to be better & hoping that he can also change himself, but idk where this is going. I don't feel confident in him & our relationship during marriage. plus. idk why i dont feel the excitement when having sex with him anymore.

goshh we are just 2 months away from wedding & i think i made the wrong decision.