Hi S.,
You are definitely in a tough predicament! I have a 20 month old son, and I did have to resort to letting him cry it out when he was 14 months old. He just never learned how to fall asleep on his own. But by the time he was 14 months old, I had tried all the non cry-it-out methods, and none of them worked! (But I definitely recommend that you try all of them first, like other posters suggested. I really did like the book No Cry Sleep Solution (or whatever) by Elizabeth Pantley. Like I said, it just didn't work for us.)
I finally had to resort to letting him cry it out because like you, I was (and still am) pregnant, and I was desperate. But I did it my own way. There is a rocking chair/glider in my son's room next to his crib. So when I laid him in his crib, I stayed in that chair the entire time because I did not want him to think I was abandoning him more than I already felt I was! I just did not make eye contact with him for most of the time. Every five minutes, I would get up, give him a kiss and hug for about a minute!, then lay him back down. He would get up immediately, but I just sat back down for another five minutes. When I got up to hug him and lay him back down every five minutes, I would give him eye contact. I just didn't do it when I was sitting on the rocking chair for those five minutes. I did try to wait 10 minutes before lying him back down, but I could never do it. I think the most I could last was 7 or 8 minutes, but usually just 5.
The first night, he screamed/cried for almost an hour. The next night, he cried for almost 45 minutes. But the 3rd night, he didn't even cry for 10 minutes, and by the 4th night, we were good to go!!! You must believe me when I tell you that my son was not the only one crying those first few nights--it broke my heart as well!!
Now that my son falls asleep on his own every night, on the rare occassion he does not fall asleep or if he wakes up in the middle of the night, I always, always go to him because I know something is bothering him. Sometimes he is sick or not feeling well; other times it is because he just needs some cuddle time. So I do feel bad it came to letting him cry it out, but it is something I needed to do with him, and everything worked out just fine. I promise you there are no long-term ill effects on my son or on our relationship because of this!
Anyway, I definitely recommend trying all non-cry sleep solutions first that other people have mentioned. And I would never, EVER recommend letting a baby cry it out before they are 6 months old. Even Dr. Ferber recognizes that babies under 6 months cannot self-soothe themselves. But boy, I tell ya, I am definitely going to try to get my baby girl (due literally any day now) to sleep on her own much sooner. It's like my mom says "The first kid is a learning kid!" No kidding!
Good luck!