People take that little label sewn into the back of their clothes so personally. When something doesn't fit, we automatically blame ourselves before acknowledging that different brands size clothing... well.. differently.
You hear your negative self image whisper, "if you weren't so fat..."
I know, I've heard it too.
Consider this: Why are you allowing yourself to get emotionally involved with a piece of clothing you haven't met until right now?
When you look good on the outside, you feel even better on the inside and it shows. Wear the size that fits and remember: When he makes his way over to ask you for your number, he doesn't care about the one in the back of your pants.