When I go shopping for clothes, I buy all my clothes a size too small thinking I'm going to lose weight. It doesn't seem to work though.
No.
And really, it's just a bad idea. You need to buy clothing in the size that you are, not the size that you were previously or the size that you hope to be. Wearing clothes that actually fit will make you look better than trying to squeeze in to clothes simply b/c the size on the tag makes you happier.