Sorry to hear that you and your children are having to go through all of that. It can be totally confusing at times. My rs lasted nowhere near as long as yours, however mine and many others all sound the same, regardless of length. Reading many accounts has helped me know I am not alone in this and it does get better with time and distance - I can attest to this. It seems we as nons have issues to address ourselves and the breakdown of my rs was the catalyst for me to work on myself. I hope my ex eventually does the same but that is not up to me, never was. I wasn't perfect either but I tried. I tried everything I could think of to improve the situation but nothing worked. If I hadn't developed depression, anxiety, physical bodily reactions around her and overall fear of her I may have recycled many times but I physically couldn't. I'm thankful now that my body overrode my mind on this one.
Its not normal or maybe it is.
Unfortunately, it seems in these type of relationships it's normal. They move on in a whirlwind and leave us trying to figure out what happened and why. There is no closure unless you do it for yourself. My daughter was affected by it as well, as was my exgf's son. My ex-wife moved my daughter across the country to "help" and now I barely get to see her. My exgf's son went to see his father in another state and never returned - he said he was afraid of his mother. It's all very sad but all very much beyond our control. Hang in there, focus on you and your kids - if you're seeking advice, I would say work on you and why you got into and stayed in the rs, stick with the therapy, get some for your kids and keep coming here to vent, ask questions and listen to others' accounts. The people on here have been awesome in helping me get through what has become a life-changing event for me. Welcome to the family - you are definitely not alone.