I'm really struggling

This will be the first Christmas as a single parent, that on its own is upsetting me, but I'm not over my ex and lately I'm crying all the time. We've been over for a few months now but it's sinking in that I'm on my own. He's moved on and hearing of his plans for Christmas is killing me. He gets our daughter boxing day as part of our agreement and he's taking her and his new girlfriend somewhere nice, I know it's stupid but I can't stop crying. I miss him. He still has feelings for me, he's told me this. But he's with her 😭😭😭😭 I wish my life was different. I feel empty