HELP HELP HELP?

 My granddaughter is having TERRIBLE mood swings and getting hysterical two or three times a day/evening. She is somewaht of a whiner ,but we are letting that run its course. This is like she is hurting almost and when we try to soothe her she says leave me alone ...We leave her alone and then she says hold me. I want milk you get the milk she says NO juice. I keep thinking it may be her blood sugar as she is not a great eater, but not sure. Everytime I bring this up everyone says it is typical three yr old behavior. I have raised two children before her and one had ADHD and it is nothing like this.  Is it possible that she could have a blood sugar problem? Her endo says her blood levels look great and she is doing very well on the suspension. I just don’t know what to do for her. I don’t want to put her in time out for something she cannot control.. but I certainly don’t want her having the upper hand at three also. She has lately complained her butt hurts inside? I think it is because she stays constipated because she is a heavy milk drinker. But I will take her to the DR. to be sure. Just wondering about the blood sugar and the obstinate behavior that she is portraying. Sometimes I think she is going to explode from the screaming. Does the medicine cause mood swings? I am at my wits end with her andI can’t stand to see her suffer any more . She is usually a very loving child and now I have a Sybil child. Whats up with this? Anyone else experience this with there children? Cherry