Thanks IAP, it helps to know what I'm feeling is normal at this stage.
Yes, I have been in a similar situation before, my H left about 5 years ago and was talking to this same W a lot for the 4 months he wasn't with me but always denied anything happened. I DB'd and he came home after 4 months. Now, all this time later I have found this letter and all these emails to this same W - I feel like the last 5 years have all been a lie.
