I don't know why, but I am constantly anxious about someone possibly thinking I'm poor.
Why make you worried about appearing poor?
I have been told that I dress too sloppily.
Feeling anxious is a natural feeling, so don't beat yourself up about it too much. Worrying about the thoughts of other people however is not something to get worked up about. It's a waste of valuable time.
Are you sure?
Pretty sure. If you're that worried, simply put a little more effort into your appearance. But don't stress over what people may or may not think.