Please help if you can....?

Please only genuine answers. People seem to see me as stupid or an airhead, its really getting me down as i never seem to fit in with a group of friends(girls) , relax, and for them to stay in contact with me.I cant really tell when i meet someone if they actually like me or are just around me to make fun of me. for example the one time i was going out with a guy, who had showed interest in me and got to know me well while we were together when he met up with me to break up starting shouting at me telling me he saw me as an airhead and always had, laughing at me.Im a pretty gentle person not good at taking people suddenly shouting& slagging me& couldnt help but get upset while i was there which made him laugh even more.even when it comes to making friends ive often been the one laughed at when im not trying to be funny at all. it does hurt me alot that people don't seem to take me seriously the way they do everyone else,even the way they speak to me.Ive stopped going out completely bec