I love mine! I wear it over one arm, although I have never tried it over the back. Tighten the strap so that it sits snug against you, not too tight but enough so that it doesn't flop around. I have an extra small and I can fit so much in it it is amazing. I am carrying mine as a purse right now as I have a hard time changing back to a regular purse after trips. Try it out and see how you like it. I have back problems and I find that I can carry more in this bag without hurting myself than I can with a purse or a regular backpack.