Don't be upset because you're chubby or anything. There are a lot of guys out there who doesn't care about shit like that and/or they actually prefer bigger girls. Personally, I don't like guys who judges a girl solely on her weight (same goes opposite, I don't like girls who judges a guy based on his weight either). It's not fair to judge people because of what they look like, it's about their personality and who they are as a person.
I get wanting to be a singer, however that takes a lot of talent and hard work. If you really want to try to pursue that, try taking lessons :-) If you're not very good at singing (my life *cries*) then unfortunately, that wont be able to be an option. Society is cruel and if a person who isn't really talented tries to be up there with the really talented, people will lash out. Hell, people lash out even at those who ARE really talented. But I think you should at least try talking to a coach or something if that's really what you want to do. I think it's important to pursue your dreams, give it all you've got, even if everyone is against you.