I'm Remembering...

Go in, but don't pick him up.
You've created a monster by going in, getting him up, getting him water, etc. You need to break this nasty habit.
I used to put a sippy cup of water in their cribs along with the favorite toy and binkie.
Talk to him during the day about how he is going to go to bed at night and you're going to put his sippy in there for him and that you don't want him to cry during the night. Tell him that you need him to sleep so that you can sleep. Kids aren't stupid. They hear you.
When you put him to bed, show him his sippy and remind him that you need to sleep.
If he cries, go in, but DO NOT PICK HIM UP. Pat him on the back and tell him softly that you love him and that he needs to sleep. Then walk out.
It doesn't matter if he is awake or asleep - all that matters is that he is in his crib - safe and sound - and you go back to bed.
If he cries to the point of throwing up, he's figured out that if he does that, you'll come running. Clean him up and put him back. Do not make a big thing, just be matter of fact about it. Always put him back. Do not let him go watch TV, or have juice, or whatever... he gets his water and back he goes.
YMMV
LBC
PS: My husband just asked what I was reading. I told him "this lady has a 19 month old who won't sleep through the night." His response: Don't pick him up.

How many naps does he have each day. If your still giving him 2 naps it might be time to drop the early one. also is he hungry? we had to feed my daughter a bowl of cereal at night before bed. nothing sugary to hype her up. usually rice crispies or cheerios. he may be hungry. I would go in pat his shoulder and say go night night. don't pick him up, don't turn on the light. maybe readjust the bedtime a little later. At his age he should be going to bed by about 8ish and sleeping 10 to 12 hours. then a good nap at lunch time then back up. he is the age where growth spurts happen. and also bodies readjust to needing a little less sleep. good luck

are you sure he doesn't have an ear infection?

He may be afraid of something in the room now that he is more aware. Do you leave a night light on?

My son got past that fairly quickly. He was quite the escape artist at an early age. At some point he figured out if he woke us up, we'd put him back in his crib and we'd go back to bed. So he just climbed out of his crib, came to our room and tucked himself in at the foot of our bed. He could sleep again once he was with us, and we never knew till we woke up in the morning.

what does

YMMV
LBC mean?

We leave a sippy of water with my 21 month old and a little toy. That way if she wakes up she has something to do. She hasnt gone through this, but we have woke up and found her sippy of water was completely gone.

Honestly mine just has sleep patterns that vary. Recently (the last month) she sleeps 12 hours through the night and only takes one nap during the day. Before that she would take one nap, but wake up at 4am every morning. She is in her own room, and I think honestly it startles her when she wakes up (whatever time that might be) that mommy isn't right there with her. What I have found recently that might be helping is I really let her wear herself out right before bedtime. We run around the whole house. We get on her bed, then get off of it. We get on my bed then get off of it. We chase daddy around the house. We do chores (I let her take the laundry off of a chair and move it to the hamper. She puts her toys back in he rtoy bins. Whatever we have to do we try to let her wear herself out. Last night she didn't want to go to bed, so I let her get up and I fed her a rice cracker, within 20 minutes she went and laid down on her own. She just needed the extra fullness I guess. Hope this helps. Good Luck!
(Oh on a side note, if its a molar he is cutting that could be the reason why. They are huge teeth that you don't see at first, but are dropping down in the gums. My daughter cut some molars in a week, but one of hers took almost 2 months.) =)