Hi Silverbirch78.
Right…where to begin? I’m in a similar-ish situation to you as in I’ve decided to stay and try to give my marriage another shot following an affair.
Short back-story, (mum to 4, married for 18 years), I discovered messages on H’s phone, confronted him, he confessed details – six month EA which turned into a PA.
He was very remorseful and begged for another chance. We discussed things and as I knew our marriage hadn’t been all that great for a while I decided to give it another go.
Fast-forward to now - we are together giving it another go but it is really, really hard. Both of us are finding it difficult as I have periods where I don’t trust him (and given the circumstances it’s not surprising). He is making a big effort to redeem himself but sometimes I worry that it won’t be enough for me. 
He hasn’t done anything since (to my knowledge!), I have access to everything whenever I want. I also know that she has sent messages to him (which I have read). Basically I think that she, (also married with children), wants to continue their relationship,
which he has assured me is the last thing that he wants to do whether we stay together or not.
The way I see it is that I’m taking each day one at a time. We have bad days but we also have good days. We can both see huge improvements in our relationship/marriage but it does make me sad that H thought that the answer to our problems was to have an affair. Obviously it’s too late to cry over spilt milk but I do have down days when this does upset me. At this point, 4/5 months afterwards, the good days tend to out-weigh the bad days.
One of the posters on my original thread posted some advice which I have been following from day 1 – basically that I don’t need to make any decisions at this point in time regarding our relationship. I’m taking one day at a time and seeing how things go. If I decide in a few weeks/a few months or later that I genuinely can’t continue in the relationship then I can still decide to end it then. Ultimately it’s going to be up to me what I decide to do with my life.
If I end up making a mistake by giving him another chance (as many posters seem to think ‘once a cheater always a cheater’), I’ll know that I’ll have done everything within my power to make things work and will have to accept that I’ve chosen to forgive someone who doesn’t deserve forgiveness.
I know that not all advice is going to work for everyone and ultimately everyone’s circumstances are different but I do hope that you find whatever you’re looking for on this thread.
Thinking of you and wishing you all the best 
P.S Sorry my post was supposed to be short and to the point but it turned into a bit of an essay! 