Feeling Invalidated in a Not So Stable Relationship

This relationship sounds very toxic. If I was your friend I'd be advising you to get out. A good partner is supportive, not vicious. As for self esteem, I have a super easy and cheap trick that's helped me immensely. I bought a 5 pack of colorful dry erase markers at the dollar store for $1. Anytime I can think of anything positive to say to or about myself, I write it on the bathroom mirror. "You are enough" "You have pretty eyes" "you are a supportive friend." Etc. It wipes right off just like a white board, and since its something you see every day, usually several times a day, its a constant reminder. When people aren't being kind to us, I think its especially important to be kind to ourselves.

Possible say in the mirror that you are doing enough, and acknowledge your progress. That is their opinion not yours. I hope this helps =)