? My friends leave me ?

Not to long ago my friends stopped talking to me and if I did something I have no idea what. I've been talking them to cinema and amusement parks but when we would be there they would go off with out me , leaving me alone =( And yesterday my 'best' friend took a few people she barely knew and my other friend to the cinema ... =( they just don't talk to me anymore , it just started up after the midterm ? Any help because really I have no friends now =( I just feel so depressed and sad