Seems like I know a lot of folks who have gone through what you are going through, and over the years the following "tests" seem to help:
The "good guy" test. Is your DH basically a good guy who messed up? If you think so, work to save the marriage. There ain't that many good ones out there IMHO! If in doubt, strike 1.
The "Can you be Present?" test. One friend walked in on a scene that she could not erase from her mind no matter what. There was no escaping the past and the relationship had to be put to sleep. But if you can get past the past, so to speak, and be present with this guy and if that feels good, go for it. This may be where counseling could help. Not sure how awful his betrayal was, so not sure how this test will go.
The "Imagine the Future" test. Spend a few days imagining a future without your DH. Does that make you feel relieved or sad? Happy or anxious?
The "are you sure what the problem is?" test. How long ago was the betrayal? Are you sure that is what you still feel hurt about, or could it be other things? I ask because you said you have trouble trusting--if the issue is more about the future than the past, make sure you focus on the future and how to feel safer about it.
Hope these help. I am new to the list so I hope it is OK to share these opinions without sounding like I know it all.