Up until about a week ago, we've had such a bright, smiley baby. She loved being talked to and would keep eye contact and 'talk' back and tell long stories with the biggest smiles. Now, all of a sudden, I can't get her to keep eye contact anymore. She just looks at the floor, or her feet, and won't even lift her head. I haven't seen a smile in days, and she cries all the time for no reason when she used to never cry at all. She no longer responds to noise. I've tried snapping to get her attention, calling for her, and I even screamed (gently) into her ear and she doesn't flinch or look at me. If I try to lift her head to look at me, she looks away really quickly or fights it and cries. I'm starting to get frustrated. What's going on?