Being good friends with the opposite sex very often eventually leads to an affair - it's very hard for anyone to have that kind of willpower - even for married people who think they would never be unfaithful. It's going to be very hard for you to make a decision, but you need someone who is going to be your companion and is not socialising to that extent with other women.
If your boyfriend is flirting with his female friends than you need to find yourself a new one, the quicker the better. If the situation is that you just can't accept them around him and feel the need to compete with them.. you need to work on your self esteem urgently. He chose you, not them :) Shine bright and make him feel proud of his choice :)
If you’re having trouble with jealousy, there could be a few reasons. Are you feeling insecure about your boyfriend’s feelings of attraction toward other women? That could be for a good reason, if his behavior is flirtatious. If you’re worried he might stray, it’s best to objectively consider whether your fears are based on his suspicious actions or your own self-esteem. If you feel inferior to other women in general, especially physically, then you can rid yourself of those feelings by building up your own confidence. To increase self-confidence, try learning a new skill, accomplishing a goal or overcoming an obstacle.
You need to sit down and have an open and honest discussion with your boyfriend. Let him know how you feel so that he will be able to reassure you of his feelings and his intentions. It would also help if you became friends with the girls as well, taht way you get some new friends and possibly some more insight into your boyfriend's life.
Be more confident in yourself. Your boyfriend choose you to be in a relationship with, not them. Maybe these female friends and your boyfriend know each other for years so it will help to accept them in your life as friends also. They could be a good source of information about his childhood and previous relationships. Make them like you and they will be always on your side ;)