infant sleep problems

Hi, my daughter is 23 months old and she always had sleep problems in the night. she either sleeps very late or keeps waking up quite often some times she seems to have nightmares and starts crying while in sleep. Iam expecting another baby very soon and i really need your help with her sleep problems. she sleeps for 2-3hrs in the afternoon and if i do not let her sleep in the afternoon she bcomes very tired by 5 PM and automatically goes to sleep for 2 hours and does not go back to sleep till 1 or 2 am. she usually wakes up between 9-10 am sometimes 11 am. she is a very active child but, does not weigh much. she weighs only 22 pounds as of now. she has normal bowel movements and her appetitite is normal.Please help me.