You're definitely not alone. Even extinction did nothing for us. I often slept through him crying out of sheer desperation.
Also, do try co-sleeping if you haven't already. There may be risks, but don't underestimate the opposing risks of never getting enough sleep. And there are easy ways to minimize the risks.
I went through the same thing, and finally simply had to night wean for my sanity and my ability to function. I wrote a book for my daughter at 23 months called Sally Weans From Night Nursing and it really worked for us. Before becoming a mom I worked as a social worker/therapist with children/families and in the book I included validation of feelings about night weaning and simply explained the process of what night weaning would look like and why it is important--so everyone can get more sleep so that than play with more energy the next day! Give it a try it you think it might help. I was able to night wean my daughter in four nights. Its on Amazon and also Kindle, www.amazon.com/Sally-Weans-Night-Nursing-Mitchell/dp/1483933830 Good Luck!! I know it is stressful!