Forgiveness is for oneself, not for the benefit of the one you feel has wronged you. But that's not really what you are asking is it. You want someone to make the decision for you whether to continue in the relationship or not. Or perhaps even nearer the truth, someone to confirm the decision you want to make but don't have the confidence to do so by yourself.
Only you can decide what is right for you. Other folk in your position choose one option, others the other. Ignore what you have always said you'd do. What do you feel is right for you now ?
For sure you need a good heart to heart talk with him. His indiscretion was two years ago, but what is the present situation ? Also, will you be able to trust again at some point or not ?
Mull it over and decide how you feel. If unsure then toss a coin for a decision, then note whether you're ok going with it, or wish to make it 2 out of 3.
Good luck.