I am very uncomfortable about my bf being "best friends" with his ex, what should I do?

oh im really sorry for u, but theres no really of a straight answer to this. U should decide for yourself what do u want from this relationship for future and what do u expect from it. U should talk to ur bf about this situation, be clear, ask for his opinion, tell him that u dont feel comfortable with her being around too much, tell him about ur feelings and stuff. if he somehow will try to get away with it, put the question differently, like either me or her, if he picks her... then idk just forget about him he's not worth it... hope it helps