What should i do? URGENTTTTTT.... REALLY NEED HELP!!!?

I dont know what to do anymore.... i have a best friend and we were close.... but just this day, we felt estranged... i felt that he's forgetting me and befriending the rest of the cl! I know that it is weird.... I mean this kind of thing happens a lot and i always end up in pain but i keep admitting that its just for a while.... and seriously i felt weak... its like knowing that the current happiness can create great pain but i keep doing it.... what should i do??? I mean im confused!!!!!!!!! seriously i need all help i can get....