No sleep anymore! help!!!

My son is turning 1 in early January and he has just started a new pattern about a month ago- every night that he wakes up, sits up in the wee hours of 12:30 am, 3am or 5 am. So he sits up, cries for while until one of us comes over and tries to lay him back down with his pacifier. Now that doesn't work anymore until I started to give him some water at night thinking maybe his mouth is dry. He drinks lots and lots of water during the day, but its very dry in the apartment from the heating. So this is my rational thinking maybe he's just thirsty? Then last night was the worst. I gave him water, he laid back down for a second then got up again screaming. So I thought, maybe because he didn't finish his similac at dinner he's still hungry? so I fed him a few ounces- which he gobbled down. I need to mention though, before I gave him the milk, I picked him up out of his crib to feed him and when I sat down he was sitting and smiling like he's now satisfied by the situation lol. This is at 3 am and I am half asleep!

Anyway, I think I am creating a bad habit here obviously, but I don't want to be a bad mom and not answer to his needs since he can't say what he wants yet.
Is there a better way to solve this so I can get a full night of sleep again?? anybody else going through this phase?