Hi [L]ing_eR,
not sure if I'm too late to give advise.
First of all, I must clearified that I'm no expert, non am I trying to influence you thoughts.
Question
Why would a bf not wanting to share his friends with his gf??

You got to let your bf know how you feel. If he had his valid reasons then try work out something that both of you can agree upon. No point playing guessing games. If things don't change for the better then think of something else. Maybe you are not meant for each other. Maybe he is the bo chap type, you are the gan cheong type.
In situations like these, you have to make your own judgement. You can find tons of advise from anywhere. 'Break off lah...', 'Talk to your bf lah....', 'Give him a chance lah....' and many more BUT ultimately, it's YOU who makes the decision.
Hope you make a good decision.