Somone keeps stealing from me! What should I do?

Last Friday I had $7 in my backpack all day, by the time I got home it was gone! I just thought I might have droped it or it fell out but this Wedesday another $5 was taken from the same part of my bookbag, the front pocket! And I just now notcied my perfume was taken too! Its getting really annoying and somewhat scary kowing someone is getting my stuff without me knowing. I'm in gym and the door locks when you leave and I'm usally the last one out and I leave my stuff un locked but where I keep my money is also where I keep my phone but that is still there and its an iphone so they ovbiously want just my money because thats all there taking! I'm also in track where my stuff is out in the open as well but so is everyone elses and no one else seems to be saying there stuff is getting taken? Any ideas of why someone might take my stuff? I assume its a girl from the perfume but i'm almost positive it wasent anyone from my gym class because there's only 4 other girls one who is like my best friend and would never steal from me and the other girls I've known since middle school and have never been known to steal! I'm not sure about track but I wasent even in track yet on Friday when my $7 was stolen so I have no idea what to do! Any ideas! Help me please! I'm so tired of people stealing my things!

You seen a ditzy type. So maybe your losing/spending it yourself and not remembering?

Get a zip padlock for your backpack and see if you still "lose" your stuff.

You should definitely report this to authorites so they can keep an eye out. Try keeping your things in a safe place, somewhere you know that no one will be able to find. Keep the money in a large pocket or a locked small box of yours. (pfft, a wallet isn't going to do anything to keep the money safe at the moment.)

You said you leave you stuff unlocked.Um, would it not be better to start locking it? Buy a cheap little pad lock and the problem is solved. Or keep your money on you, such as tucking it in your socks. Or leave it behind the hip band of your underwear. I know that sounds weird, but at least you know you have it.

Also, start reporting these things. It may not be a kid, it could be a janitor or a teacher. I know I read somewhere very recently that a gym teacher was caught digging through people's backpacks.

*EDIT*
Also check your bag to see if you have holes in it.

So you just keep leaving stuff unlocked, and it just keeps getting stolen, and you keep leaving it unlocked, and you can't figure it out. Really? You need help figuring out what to do?

Lock everything up and check on Your stuff constantly, also, you should report this in your school