I assume you mean you have an I9100T ?
1) The reason your recovery isn't sticking after you reboot is because recovery is 'baked' into the kernel on the I9100, so any recovery flashed independently will only persist until the next reboot.
2) Do not use Rom Manager with the I9100. At all. Ever.. Eventually, it will break recovery & cause your phone to reboot. The only fix is to flash stock via Odin & do a factory reset. And as most people here don't make regular backup, it sucks to be you in this situation because you lose your data.
3) Easiest way to get CWM that will stick is to flash a custom kernel; you have several options, a search will reveal your choices (PhilZ seems to be what many people use these days for simplicity's sake). From there you can then flash whatever custom rom (or kernel) you want.
If you don't have an I9100, clarify exactly what you have & we'll organise mods to move your thread.
If it's important enough to cause you grief if it's lost, back it up. No excuses
Trolling for thanks is lame
Does Samsung's auto-brightness implementation crap drive you to self-harm ? A solution !
Failure to search is the leading cause of male impotence on XDA
If you don't know how to recover if things go wrong, what are you doing flashing custom roms ?