Should I give up or fight?

I have been best friends with this guy for a year now. We've gone through everything together. We've stopped each other from crying, give advice to each other, literally saved each other's lives, and just made each other happy. We loved each other so much. I still love him... so much. Last month, we got into a fight and didn't talk for a week. It was a record. He started talking to another girl and she basically replaced me. He still says we're best friends but I don't think he sees the fact that I'm lucky to get a conversation with him once every 3 weeks. I asked him what happened and he said he really has no idea. I don't know what to do. I don't want to give up on us, but I don't know if he even cares anymore. He used to always talk to me first or try to talk to me, but now he doesn't even care. He talks to so many other girls that don't include me. What should I do?