I think that when you get to piecing it is quite common for all the hurt to start coming to the front. Everyone has to deal with it differently. I read a lot about infidelity and healing from it. There are some great books out there, and some you can share so that your S can understand what you are going through.
Really you need to play this by ear....as each S can react differently. My H was luckily very open about everything and would talk to me about it all....others are so ashamed that they just want to sweep everything under the carpet and forget about it all. There are no firm rights or wrongs.
What ever though, you both need to be open and honest and 100% transparent in your dealings with one another, and others. No walking on eggshells....no changing your true feelings just to suit your S. Obviously that doesn't mean don't be diplomatic and take each other's needs into consideration etc. Focus on the future and always try to have something nice planned for the future.
I think you will find you have this 'honeymoon' period and then things may well backslide. Just remember not to fall back into old bad habits - have a date night once a week or so....do things to keep the R fresh and fun. There will be ups and downs...but that's life.
Good luck. I honestly believe that what you do in piecing is really the template for the rest of your M.
Saffie me 46 H 46 M in 1986 D20,D18,S16,D13 H's A 01/05 to 07/06 H recommitted to M 07/06 renewed vows 09/06 Going from strength to strength
