Most Helpful Girl
Follow your heart. Despite what we tell you still have to deal with the consequences. If you still have feelings for your ex then it is not fair to your current spouse. You cannot drag her along while you're trying to figure out what you want. I feel you should tell your SO what's going on and ask for a break. During that break you should think deeply about which girl you want
Most Helpful Guy
It can work out since such a long time has passed since you dated, also since you only dated for 2 months its unlikely that you fully knew each other and can say for sure if you are compatible or not.
However given your specific circumstances i would not take that chance, since you already are in a relationship with a girl who hasn't let you down in terms of trust. The ex gf however since she has already betrayed your trust once its not that unlikely that she could do it again.
by the way was it your ex that got in touch with you after 2 years of no contact? what did she say, did she apologize etc?