Terrible Threes??

Not that we haven't had our challenges with Macie, but the last week or so she has been totally out of control! When she is at daycare or with someone else, she behaves pretty well. Then I get there and all hell breaks loose! Today, for example, she was whining from the minute I picked her up. When we got home, I gave both kids a snack and some juice. I also turned on Mickey like I always do. Nothing seemed to satisfy her. She started screaming and throwing a fit (about what I'm still not sure). After trying to reason with her, I finally picked her up, put her in her bed and shut/locked the door. For the last 10 minutes she has been screaming at the top of her lungs, banging on the door, and jumping up and down. I can honestly say she has NEVER done that before. I could make a million excuses (she's been sick, I've having a new baby soon, etc), but there is nothing that can justify this behavior. I don't know what I am going to do, but I have to be strong. Lord, help me!