Do other people have a bad Body Image?

So... I need to know some honest opinions. I have always felt.. bigger than most. I am not comfortable in my body and always hide it behind large clothes. When I buy clothing, I am shocked to find I always fit in the smallest sizes. (This confuses me because I see girls way smaller than me.. and where do they find clothes?) When I see bigger girls that are confident with their body I am jealous. I am around 5'8'' and 120 lbs.
So it confuses me when I see myself so much bigger than girls who fit into bigger sizes than I do.
I do not have an eating disorder (I probably eat more than most).
Is this normal? Am I bigger? I know there isn't a picture to match, but any suggestions?
Do other people have a bad Body Image?
Post Opinion