My two best friends might be toxic

I have these two internet friends that I've known and talk to daily for over a year now. They are my two closest friends and the people I ineract with most. Ecspecially now that we are in quarentine. Recently, though, they've been making me feel awful. Let's say their names are T and R. T teases me a lot, sometimes crossing over to straight up bullying territorty. And, R always defends T whenever I get upset about it.

For example, just the other day, I was struggling with an essay and T said she could help me since she's good at writing. The three of us get on call and I screen share so T can see what I'm writing. While helping, T keeps making comments about how bad I am at writing. Laughing at all my typos and making sarcastic marks about "what a great writer I am". At one point I snap and tell her to shut the fuck up. T gets upset and R said I was too harsh and in the wrong for insulting someone who was helping.

Today, T private messages me and tells me about all the things she working on for R's birthday. It's coming up and we plan to watch R's favorite movies together on that day. T has drawn her art, made her an online card, and is telling me about the present she's going to ship to her. I got extremely jealous. For my birthday I had gotten a 'happy birthday' message in the morning and that was it. No presents, cards, nor did we hang out for it.

And I went all out for T's birthday, I also had a lot of stuff planned for R's birthday. When I told T about my jealousy, she brushed it off and kind of said it was my own fault for not saying I wanted to a groupcall on my birthday. My heart just dropped. It really feels like R and T like each other more than they like me. I don't know what to do anymore because they are the only two I really talk to.