My 22 month old still gets up every 2 hours--what could be wrong with him?

he expects me or his daddy to pick him up and rock him to sleep..sometimes if im lucky if i give him a pacifier and pat him on the he goes back to sleep. hes never slept through the night once yet since hes been born. he wont go to sleep until 11:30 or 12 at night. and gets up "officialy" at about 7 or 8. he takes one nap in the afternoon for about 1.5 hrs at about 12:30 or so. ive tried not letting him have his afternoon nap but he just gets really grumpy and tired and just falls asleep later anyway and then he gets up again after 1.5-2 hours and then it sucks b/c now he doesnt go to sleep until 1 or 2. so im left with letting him take his afternoon nap so at least he goes to sleep at night around 1130 or 12. its the hardest thing ever to get only5 hours of sleep everynite and even that be interrupted every couple of hours. ive mentioned it to the doctor at every well baby visit and they alawys say just let him cry it out--ive tried that and he just screams and starts throwing up and cries for hours on end. he is healthy otherwise--not hungry or anything.he walks and runs and he has about a 40 word vocabulary (no sentences yet) although he doesnt use any words on his own- only if i ask him what is that---he will tell me the word but otherwise he just pulls and points. its too embarring to mention to the doctor anymore and i dont know what to do. any advice?