I don't know that I can add much to what the previous replies have provided you. I agree with SiN. Open dialogue is the way to address things.
I went through this with my now ex-wife and if I knew then what I know now we might perhaps still be married. There is a line of thinking that says that there are usually five or six most important emotional needs in a relationship that when met will prevent infidelity and promote a healthy relationship. Following the official end of the marriage I've done a lot of reading and thinking about what I might have done differently to create a better resolution. I won't go way off topic here with that story but I do want to share one site that is very helpful in providing advice on how to approach this situation.
The site is called
MARRIAGE BUILDERS.
I hope this helps and as the saying goes ... trust but verify.
Best wishes.