How to stay confident when you're losing all your friends one by one?

I am at a step of my life when everything is harder than before because I never felt so alone.

I came back from Portugal in September after spending 10 months there working in a call center. I made two close friends there among other encounters. Today I don't have any contact with these persons anymore. One of them was my roommate, and he inexplicably stopped answering my messages few months after I left Portugal. Yet, before I left he was asking me not to leave and kept on telling me that I was one of his best friends and that he rarely had such connection with someone. The other one was a girl that soon turned out to be the most passionate friendship that I had, but it ended up in a nasty way because our relationship was too toxic. Even though I'd like to get in touch with her, I know it's not the right thing to do.

Before this trip I lived in france near my 3 best friends. I'm not the kind of girl to have lots of friends, hard for me to connect with people since school bullying episodes. I'm getting over it with time and efforts but it's still an issue.

Anyway I also have a close friend in France that stopped talking to me eventually and it hurts because she's important to me. And right now my main concern is that one of my best friends is also starting to lean away from me. I'm not going to say that I don't know why because I do : I'm always negative and depressed and it sometimes prevents me from supporting people when they need my help (REST IN COMMENTS)