So sorry. My WH is the same way about communicating, plans his trips and sometimes remembers to tell me about them- or else I hear him talking to someone else about it and its like "Oh, you're going to XXX?" He's always been that way, so even though he used his trips this year to meet OW its not a HUGE trigger for me, just another reminder of how he is, and will always be.
I was separated for 7 months...I did find that despite the sadness (Which. lets face it, was unavoidable whether he was there or not) I was still able to recognize how I might be happier without him around! It made me realize I had always had to take care of myself anyway, nothing really changed except I had one less kid to pick up after, and I sure didn't miss his negativity and criticisms!
So when he came back home, although I did enjoy remembering the good things about being together (Which I had honestly forgotten), I also am determined not to put up with the bad/annoying shit that I now have opened my eyes to. Be prepared- being around him again made the pain/hurt/anger all new and raw again, when I thought I had begun to grow a scab. I posted about it under reconciliation forum, subject was something like "Attempting R-makes pain new again" and I got some great replies, you should check it out.
I'm sure you're scared. After 4 months of processing this on your own (sorta) you are now going back "into the fray". Go back with your eyes open and take your time observing him. Just because you ended separation doesn't mean you have to make a final decision yet. Love yourself! and that new baby :)