i'm thinking of buying everything oversized.
Would wearing oversized clothes make you uncomfortable?
Yeah, but wearing oversized makes me look like I am cold even though I am not.
It seems that you don't actually like the way that oversized clothes look. You should wear clothes that make you comfortable and clothes that feel cool to you, not others. If you wear a style that you don't like it will make you feel insecure and less confident.
I guess. What if my clothes are too small
It could happen but you can play around until you find something that you like and are comfortable with. You need to be happy with what you are wearing.