Messenger bag help

[Tri Girl]

OK- stupid question for you ladies. I've never worn a messenger bag before, but I hate my backpack (too bulky on my back) and I wanted something new. I don't know how this is supposed to look. I took pictures to see if you think it looks right. There is the big strap that has a padded part on the front, and a smaller waist strap that clips to the bag to keep it still. Is this how it's supposed to look when on? OMG- hello boobs! I have to have the main strap that tight or it falls off my shoulder, but I think it doesn't look right.

Don't mean to ask such a dumb question, but I'm still fairly new to commuting and really hoped the bag would come with instructions for dummies like me.

Thanks for your help!

This is the bag: http://www.titlenine.com/shopping/pr...ProductID=2355