What am I doing wrong!! HELP!!!

I do not know what I am doing wrong; but Sonia will NOT sleep in her own bed/room. I lay down with her and rub her back and when I try to leave she starts crying and says her belly hurts and she needs to throw up. When we arrive at the bathroom she cries and says she wants Daddy and to sleep in Daddy's room. Now, I have been laying down with her for almost an hour and I thought she was a sleep but NO!! I get extremely aggravated because I am tired and she used to be fine going to sleep after I left her, but ever since about June of last year she has had to have me lay down with her until she has fallen asleep. I don't know what to do. I have tried all my "tricks" I think I know but they have not worked! HELP!