I'm so sorry to hear that sr - I have been there too and I understand how that feels. Please keep posting and do take your time in thinking about how you want to move forward here.
For now, I would look after yourself and process things. Also, do have a think about boundaries. If an A is ongoing, I would suggest to reduce any interaction with him to coparenting. Pleasant, minimal and he doesn't get to spend time on your couch sipping wine and chatting - but that's JMHO.
Did he disclose the A to you directly, or did you find out about it another way?
((((Big hugs to you))))
T 13 M 7 Me 48 H 46 SS 15 BD 7.14 PA D final 5.16 (H filed)
We receive & we lose, and must try to achieve gratitude & embrace with whole hearts whatever of life that remains after the losses - Dubus