is it completely unreasonable to be jealous of my bf's facebook female friends?

[gator_ce]

As a male, when faced with an insecure female, I view that is their problem and not mine. The fact that he is adding attractive women is not really the problem. It would seem that even if every girl on FB was ugly, you would still have an issue with trust.
You do not mention any reason for being jealous, you simple state that you are. Your boyfriend is not responsible for the lack of self esteem, which is often at the core of jealousy.
You may wish to examine that aspect of the issue before worrying about your boyfriend. In the long run, for a man who is not included to cheat, Jealousy is like an accusation and unpleasant. You are punishing him for a crime he may not have committed. That can only lead to him pulling away. The vacuum in self esteem is a void only you can fill. It sounds like instead of focusing this energy on this non-productive line of action. The best thing for you would be to seek consultation for this issue. until that is under-control you will never trust others.