Every time I turn my macbook on it gives me a flashing grey folder with a white question mark on it. I heard I need to put the startup disc in it, but I don't have a start up disc, I can't find it. Am I screwed? Is that it?
Maybe. Do you have any backups? If not, there is a chance you're screwed. You can always try booting a LiveCD version of Linux to grab the files if the installation of OS X is messed up. If the hard drive itself is messed up, you probably won't be able to get the data.
That said, have some hope as you could have a startup disk setting that was changed. Have you tried reading this: http://support.apple.com/kb/TS1440
Also, what version of OS X are you running? Lion 10.7? Snow Leopard 10.6?
If the safe boot and PRAM resets don't work and you don't have the install disc to run Disk Utility, you can boot to single user mode by holding +S on startup and letting go when you see white text on a black background. At the command line prompt type /sbin/fsck -fy. Reference: http://support.apple.com/kb/TS1417
If you need to reinstall or format the drive, Mac OS X 10.6 is still sold, so you can purchase a disc for $29 U.S. if need be, or if the computer is less than 5 years in age you can order replacement discs of $16 each from AppleCare.