The holidays can be hard — I’m sorry you had a lonely Thanksgiving, LW.
But, I also don’t see a problem. You may be in a committed relationship, but eight months in with his divorce in the not-too-distant past and with kids in the picture, I don’t think it’s a big deal that he didn’t include you in his plan (which he made when you’d been dating just a handful of months). This isn’t a reflection of his feelings for you and if you haven’t even told him how you feel, it’s not really fair to say he’s dismissing your feelings. You thought you’d feel okay spending the day alone but you weren’t… that’s okay, but it’s not his fault.
“If I were not in committed relationship with him, I’d see other people, and probably would have made plans, most likely.”
You “probably” would have “most likely” made other plans if you weren’t in a relationship? I mean… to me this kind of reads like you were expecting a committed relationship to save you from the life you have. But you can be in a relationship and still live your own life. What did you do for the holidays last year?
However, if you feel like you’re not getting your needs met in this relationship and there are other instances in which you have felt disregarded, that’s something to think about. But you should talk to him about how you feel.