A.W.
Hi Lindsay!
Wow. We are going through the exact same thing!! I have a 2 1/2 year old boy and a 3 month old girl. I recently sent a Mamasource request because my son was throwing a fit at bedtime and needed one of us to lay with him until he fell asleep. Well, since I wrote, he has also started waking up multiple times during the night, and his crying usually wakes up the baby (who was normally a good sleeper). So now I'm up with our daughter, and my husband has to get up and go lay with our son. The last few weeks have been horrible and sleepless.
One mom suggested to me that it may have something to do with molars coming in, and lo and behold, my son is cutting 2 molars at the same time (starting right around the time bedtime became so difficult). Of course, the moms who think it may have something to do with the baby may also be on to something, because it's possible our boys realize now that the new baby isn't going anywhere.
Most of the moms suggested that we do the whole "walk them back to their bed without speaking or eye contact" method. I would suggest starting it on a weekend! It's so painful to hear him crying for us before he finally cries himself to sleep, but we're making huge progress. On the first night, we spent about a half hour walking a crying toddler back to his bed. Then it took another 10 minutes for him to stop crying and go to sleep. When he woke up in the middle of the night, it took about 15 minutes of it to get him back to sleep. The next night, he only came out of his room twice and was asleep in about 20 minutes. When he awoke in the middle of the night, he immediately went back to sleep after I walked him back to his room. Last night was our third night, and while he still cried in his room for about a half hour at bedtime, he never once left his bedroom. He slept through the night for the first time in weeks! It's hard, but it really seems to work.
I know just how you feel. Best of luck and may you never run out of coffee.