What is wrong with me? am i socially withdrawn? please help.?

well...lately ive been spending a lot of time in my room listening to music, i don't like to go out. if people invite me anywhere i don't want to go. when im going to talk to someone i have to rehearse what i will say in my head. i always feel im a nuisance to people, even though i hardly talk, i think im a nuisance because im sooo boring now, i used to be all lively and happy and nowadays people notice that im boring. my mum doesn't notice because i can talk to her..whats wrong? thank you:)