Blindsided, I know how scared you are and it is normal. I know you feel as though you mean nothing to him and that is how he is treating you. Everything you wrote in your post it normal and I felt and feel it all too.
I think you need to stop looking for reassurances. There aren't any. He can't give them to you and the more you look for them to more he's going to insist it is over. Stop giving him reasons to confirm this! You'll just disappoint yourself over and over.
Three days is not really a lot in the grand scheme of things. I know it's hard, but each day will get easier. I promise this. You'll have a bad one here an there but they will get easier over time. You have to focus on you.
Stop thinking that he is "going off into the sunset with the OP". That gives the impression that there is some movie ending to this where they live happily ever after. Life doesn't work this way. Today or tomorrow is not the end of things just because it's one more day you didn't talk. It's a bump in this very long road...and there will be more! Remember...YOU are carrying his baby, YOU are the one he connected to now for life regardless. You know the stats on the affairs...let it play out. The odds are in your favour....have faith!! I answered your questions to me on my thread. J~
M 35 H 29 M 4 yrs T 9 yrs D 3 S born 10/19/07 Bomb 09/10/07 Separated next day OW - broke up and H moved out 09/07/08 Status - still figuring this out