MrsM - you ahve tried to save your marriage and your DH isn;t prepared to do the same.
I don't want to hurt you, but I would bet my bottom dollar that they are still having an affair. Everything points that way.
He is frustrated with you because he wanted his cake and to eat it, but you are being difficult.
I wouldn;t ask him to leave, I would tell him.
Black bags on the doorstep convey a very clear message!
You have tried and I do understand how much this all hurts - been there, done it etc etc
You will get over this, you really will - but not while you think there might be a chance of rekindling your relationship with your arseh.
It may well be that after a period of reflection for both of you, it might be possible to get back together again (sykes on here did that), but to achieve that he has to completely give her up and at the moment I think he is a long way away from making that break!
My heart breaks for you as I know how much this all hurts, but don't make the pain worse, start taking the right steps for yourself and try to rebuild a life that you can be proud of rather than this tawdry, sullied life that your arseh has flung you into!