6 month old sleeping tips?

My baby is about to be 6 months old, this is my first child, and i think i've gotten myself into a sticky situation. My son will sleep for four hours the first time I put him down at night (maybe, but not always!) then he wakes every three hours like clockwork. (lately he's been waking every 2 and 1/2 hours!) Also, he will only sleep that long if he is swaddled. (When he cries for me, i go in his room, and hes out of the swaddle.) This is the only way! If i don't swaddle him (or hold him like i do at nap time :[ ) he will not sleep longer then about 20 minutes. i tried the "cry it out" but he is quite stubborn and i'm not comfortable with how long he can cry and cry and cry. I want him to sleep better so i can be happier during the day :(