I don't want to let my borderline get in the way of my relationships.

My best friend went out with another friend yesterday for dinner. I saw the pictures today and it made me extremely sad. I felt betrayed for now fcking reason. I just. Don't understand why I'm like this. I'm jealous of the other friend who got to spend time with my best friend. I also felt extremely hurt when my best friend made the same kind of jokes with other friends that they make with me. I just.... I can't share my best friend with anyone. I feel so toxic.