ummm, what exactly can i do? i mean if you already know the button sequence, and you can't pull off the combo, then all i can do for you is call you an idiot.
naw man, timing is key. Just go get a hotpocket or something and return, with confidence.

yea my timeing is just off. do i just push the buttens in that order slowly or try to do them fast right after the other? and do i have to push the joystick in any direction?

pay attention to the button sequence AND the fighting stance.
if the button to be pushed is X, DO NOT push ->X or <-X, that can prevent you from doing the correct move.
Also, if you find it hard to make contact with your first punch---this often happens because your opponents stance is sorta crouching---then just sidestep and start the combo hitting them in the back.
timing is key, i cant tell you how fast or slow to push the buttons. Watch the character, some sequences are fast and others are slower...the ones that piss peopl off are the fast slow all in one combo...

ok i took some time away from it and came back and now i can do it, Thanks for your help