Don't get too downhearted! Bear in mind that different circumstances lead to different problems. My dh and I have been together for 15 years this year and married for 10. We think that things started to go wrong about the time the children were born, so we had a couple of years of things brewing before the affair, and some of the things we are struggling with now are things we should have sorted out right at the beginning of our relationship, that have slowly soured over the years.
I guess I'm saying that what we are trying to put right now is much more than just the fall out from the affair.
I don't believe that people just start affairs for no reason (but then I'm not one for believing that anything happens without some reason), so there probably will be some underlying things for your relationship (or maybe just in your dh's life), but if generally things were good in the near past, then it may take you a shorter time to feel OK about things than it has me.
I've certainly stopped torturing myself about what they might or might not have done, and I have slept fine for some time now. Also I am confident that I am a better person, in pretty much every way than the mistress, which helps (I may be deluding myself!!).
Concentrate on the fact that you are working to make things better, try to persuade yourself that you are in control, and do treat yourself, even if it is to very small things. It's important that you know you deserve the best.
Finally, if you are in the public eye a lot as a couple, then you might want to think about a story to explain why things are difficult at the moment. As with the children, I am sure that you don't want to lie (probably not compatable with your position, or I am guessing with your ethics), but if you are going to be doing things differently for a bit, and the potential for you to be upset is still very close to the surface, then you will need some sort of cover. Is there someone who can put out a general "please be nice to hha and her husband?" without being in any way explicit?
You may find that all sorts of occasions where you would have been fine (like weddings, or christenings, family parties, summer gatherings etc) will be quite painful for a while if you see happy families or couples, so don't be surprised if your emotions are very haywire.
Take things one day at a time, and again, one way or another, they will get better. Wishing you lots of luck!