Starting Low contact (we have a child together) again

I feel awful. I just had sex with my ex husband who has a serious girlfriend he lives in. So many things are going through my head right now but I feel used and degraded and so disappointed in myself. I will start low contact again with only necessary communication regarding our son. I know deep down I was hoping this would somehow prove he doesn't love the OW but it made me feel even more like he must because he felt
So guilty afterward. I've read all the articles on the OW and know I need to think of her with compassion rather than jealousy because
She's probably going through what I did. Anyways just felt the need to share with someone and get support
Being alone during Christmas is hard for me. My parents are
Across the country bc my dad just had a major surgery to remove
Part of his pancreas. He has cancer. That's all for now. Bless everyone here! Thank you for reading.