Why is my 20 month old still waking up at night?

I have a 20 month old toddler who falls asleep around 9pm every night. She sleeps good till about 2am then my husband and I are awaken to her screaming in her crib till we go to her. Then she either wants in my bed to sleep or down stairs on my couch with me. I try to put her back after I rock her but as soon as I put her down in her crib she wakes up screaming no no no. I need some help my husband and I are very tired of this every night. PLEASE HELP US WE ARE STARTING TO THINK WE WILL NEVER GET SLEEP AGAIN.