M.N.
This is tough but I think you might need to consider trying the "crying it out thing" for just a couple of nights. Believe me I know it's difficult. But in my experience with my little one 2 nights is all it ever takes whenever he develops some new sleep problem. I look at the clock when he starts and give him 15 minutes. That's my limit and usually he's back to sleep in 10. Good luck. I'm also wondering if you have tried putting him in a sleep sack? My son is 16 months old and still loves his.