Please, please, please take the advice given here and get some help from family for you to get some rest. You will feel better and be amazed at how much easier it is to cope with sleep problems. Explore the medical routes suggested here.
Leaving a child to cry is one of THE most damaging things you can do to a developing brain. A child who is left to cry alone will fall asleep but the the brain has learned that the world does not care. Automatically and regardless of all other interactions, the harm is done to emotional responses, tolerance to emotion and even recognition of own emotions.
Parents who have tried this will say that letting your child cry is extremely difficult for them, it causes stress and distress to the point where some mothers leave the house when their child is crying. If something is this distressing, why do we not listen to our instinct and act? I love kwhite's words, "sit quietly with your motherly intuitions." If you are rested, and do that, you will learn what the tears mean. Please, please give your daughter an emotional and physical connection with you now. Exhausting, perhaps; worth the time when measured in a lifetime, absolutely.
Sorry to sound preachy. This is near and dear to my heart and has really struck a chord.