I'm so sorry that this is what you've found out. I'm not at all surprised that he's trying to gaslight you though. Deny, deny, deny....then the I love you but I'm not in love with you crap. I also do not think you are blowing air up your own skirt either....he was not committed to working on your M if he was having an R with OW/'s.
This is the time to stand up for yourself. So, are you going for a D immediately, or are you going to give this some time and separate to see if #1 you really want a D, and #2 he gets to see that the grass isn't greener on the other side. I wouldn't be at all suprised if find that in a few weeks/months he comes running back to you.
Once again, I'm so sorry for the pain you must be in and the anger you must be feeling. The only upside I can come up with for you right now is this....now you know the truth. Now YOU can move forward.
Hang in there...we are still here for you if/when you need us.
