Tonight I was riding and I began to hear a scraping noise...when I got home, I noticed my back tire was pretty low, and it was rubbing against the back brake. I wasn't too worried, but when I lifted the bike and spun the wheel, I could see it wobble a little bit, AND it was hitting not just the brake, but also the frame! Oh GOD...is it ruined? i don't know what I did??!!

I've been trying to fill my tires...I must be stupid or something. I KNOW there is no air going into them when I pump the air pump. I just don't know what I'm doing wrong. Now I'm terrified that my wheel is damaged because my tire was too low.

Can this be fixed? Oh please tell me it can be fixed!!