Is there a way to save my friendship with my best friend?

I have been with my girlfriend for three months now and things are going good. The other day, my friend flipped out on me and cursed me off and stuff. Apparently he really likes my girlfriend, but he never told me until now. Its been three months and now he decides to tell me that he really likes her and he has known that my girlfriend and i have been together since day one. He said the only way he would be my friend again is if i break uo with my girlfriend, but i wont because we both have feelings fir each other. If he would have told me that he likes her, then i would have never asked her out. Whk is right in this situation, btw we are both 15.