I don't have any magic cure or fix for what you're feeling...but boy-o-boy do I know EXACTLY how you feel.
Similar sit, H cheated, lied, ended it with OW, we never separated...are as you say
"....together now and things are going well, he tells me he loves me and we are planning a good future."
This time of year is very hard for me, the bomb dropped about 13 months ago for me-when I found out the whole truth about PA; and the PA itself happened from Sep-Dec 99. I still sometimes drive myself nuts thinking 'I wonder if they were together today' and other various thoughts that I know you are very familiar with.
My H knows it's hard for me, and sometimes I can see more of an effort from him but he wants to just move on and get on with our lives as if it never happened. I wish it were that simple.
Are you able to talk to your H about how you feel? Not asking specific questions about what they did etc., but that you know it happened during this time and you are feeling bad. If he doesn’t get the hint then maybe just tell him you need reassurance from him.
Hang in there...try to busy yourself and not think about him and OW,I just keep telling myself that 'he’s here'...'he's with me'.
Some days are better than others. Do you have kids? I find that trying to busy myself with them and gearing the holidays towards them helps as well.
Anytime you want to vent...vent here-cause I really do ‘know what’cha mean’.
