"he says he cant go on with me crying & questioning him daily"
And can you go on like this MrsM? I don't 'know' you, but I wholeheartedly wanted to echo SoupDragon's comments and proposed questions.
I have been through this and know how frightening, confusing and soul destroying it can be. You spend so much time thinking everything has changed and how can you go back, or return to some semblance of normal? The simple truth is that this just isn't possible. Everything has changed, but the thing to do is to get to a place emotionally where this is a good thing. You don't want to go back to how things were before the affair because it sounds like both of you were unhappy.
I think- unlike some of the cases on here- you might just have a fighting chance of things being as good as if not much better than before. You have chosen to stay together, the first hurdle. You say you trust him not to do it again, the second hurdle.
You say that you keep crying and questioning him constantly, and yes I can see how wearing this is for him (more so for you of course) but this implies that you are still trying to get him to see your side of things. Do you feel like he really understands what he has done to you, how hard this has been and how scared you are? As SoupDragon said, you must sit down and tell him openly (tell him you hate him, tell him you love him, tell him the irrational thoughts you have, your fears) everything that has been on your mind. It is not until you have told him everything and feel happy in yourself that you have explained the depth of the problem that you can draw a line under it and move on. The first step with moving on will be for him to change jobs. I am sorry, but that is his punishment. I don't care how much he loves his job, you will never, ever accept that she is still a part of his life. All contact must be severed. It is alright for the shadow of her to be there in your past, by rights it should remind both of you how close you were to losing what you have, and hopefully help you pull together to prevent it happening again. It is not alright for her to figure in your future together.
I am the happiest wife I could be and I used to be where you are now. If you want this to work, it will. I'll be thinking of you, I know how hard it is. Make sure he listens to the words you are saying and that he isn't just dismissing it all as symptomatic of your emotional state.
Oh and when you've told him everything on your mind and asked all the questions you want to, let him do the same. It may be brutal and it will hurt but you must hear it all now if this is going to be fixed eventually.