M.,
I went through the same thing. Actually, my little 22 month old still does the screaming routine. It got to the point only I could put him down which did not allow me to leave the house or leave him with grandma. (And we moms need breaks). My husband finally intervened and although at the time I resented him, it was the best thing for all of us. He made me leave the house at nap time one long weekend. He let our then 9 month old cry it out in his crib. The fist day it took an hour, the next 30 mins and down to 20. At night my husband held my hand or hugged me or took me on a walk around our property. I know a lot of moms on here are against the CIO routine. On a personal note, I was in counseling for an unrelated issue and shared my heart ache during the crying sessions. My counselor said my husband did the best thing. My rocking and consoling was only creating a co-dependant relationship.
The following weeks, I took a shower at nap time. The screaming only lasted 10 or so minutes and he actually started sleeping longer than 45 mins. Up until then he would sleep 45 minutes, wake, I would rock, and maybe get another 45 mins. Today, he still screams once or twice a week for about 10 minutes. After some reading, I learned it is just how he unwinds. I have also learned the cries are different for dirty diapers and illness coming on. So, I know how hard it is, I would cry while he cried that first week. Now, when he stays with grandma, he goes down with no fuss and sleeps through the night. We can take him anywhere and he goes right to sleep. Also, one of my biggest allies in the sleep battle is strict schedule. (which is not in my nature.) When his scheduled is varied the screaming starts, which is okay he needs to learn flexibility, but I try to build in that flexibility in a controlled environment.
Anyway, I have prattled on enough. I hope everything works our for you. I know how exhausting it all can be.
Blessings,
M.