am i weird by feeling this way? details below?

well, my friend A and B were best friends. when they are together, they would always make fun of me. I know they didn't mean to hurt me or anything, but I really hated it. And lately they kind of separate because A moved school and she made a lot of new friends. So for me, my only friend is B now. But unfortunately for me, B wanted to be best friends with A again, which they are now. They just aren't as closed as they used to. And I'm just selfish and don't want that to happen. It's not like I don't like them or anything like that. They can be great friends . It's just that when they are together I feel upset. I feel like they will take each other away from me. I'm scared that they will go hang out without me, they will talk behind my back. I'm scared that if I tell A one thing, A will tell B. And if I say anything mean about B, B will get angry at me and A will stand by her side.
I'm just so scared that they won't like me anymore, I don't even know if they do now. I'm scared that A will be taken by B, and B will be taken by A. I don't know what's wrong with me. Am I going crazy? Someone please help?