I am not sure I will ever be able to believe in and/or trust anyone 100% again. But I have learned to believe in myself, no matter how fallible I am.
I have a big mouth and I remember telling my girl friends-- pre A- that "our' marriage works for us and blah, blah, more know it all crap that burned my ears to think about for a long time. I sure was wrong.
I am better informed now and I am not sure I would trade that back for my naïve assumptions about him and us, even if I could.
When you know better you do better. As other posters have already addressed his actions will show if he can make changes over time or not. You don't need blind faith. He had one shot at that and it is gone forever now.
As others have said your antennae are up and know the drill. If you are willing to make it a go with him again, you can cut yourself the same slack.
Loving someone and being unable to pick up the red flags with your rose colored glasses is something that many people have done. In some ways, it is a credit to you for being able to extend that level of trust and belief in your spouse.
A wayward earns trust back a little at a time. Perhaps that is the same for ourselves. Over time you prove to yourself that you can handle whatever comes down the pike.
I am a full believer in the trust by verify attitude. For as long as you need. Privacy is for the bathroom. That's about it. I have not verified in a long time. I'm 6 years out but if I want to go into his work email tmrw, I will and feel not one bit itchy about it. And to his credit, he could care less.
You have every right to be looking... Over time (that dang dreaded word), your gut will settle if he is doing the right thing. But I have to say that the coolest thing R and working on me gave me, was knowing that even if I did miss it all again, I am going to just fine. I am my own person now. I never took the time to do that before 40. I'm a slow learner.
Trial by fire. Box checked.
Hang in there.