20F and 21M

I’ve been in a long distance relationship with a 21M for almost 3 years now I believe. We were very depressed and lonely before we met each other. Throughout the years I have struggled with feeling like he loves me even though he reminds me all the time. I have big jealousy issues, which I think is toxic or unhealthy. I tell him I’m not healthy but he still accepts me.

Well recently he met a girl online. And all he does is play online with her and chat and vent to eachother. He told me she was just as lonely as he was when he her age. He told me he feels protective over her and he makes her happy. She started calling him her brother and he wasn’t so comfortable with it but he likes to play with her. We been in arguments for days, not bc of the girl. But I feel a bit jealous even though I shouldn’t bc he’s been giving her more attention lately. He said it’s bc I’ve been busy with work and I’m in a bad mood all the time. I get that. But when I wanted to talk seriously with him about us after another argument, he told me his friend is mad he took my side and left her to talk to me (bc he’s been talking to her about me and she doesn’t like me..) idk what to think but I feel uncomfortable. I can’t tell him to leave her cus he doesn’t have other friends and he’ll be sad. But he talks about her like she’s one of the most important people in his life or something. Am I exaggerating or be concerned.

When I was talking about my feelings with him in text, I found out he was playing with her that’s why he was responding slower than usual. I know he’s been quite depressed, but idk if I should just chill out?

TL;DR: Should I (20F) be worried about my bf (21M) new friend?