My DD had her 12 week jabs Monday lunchtime. For the last couple of days she's slept an awful lot - very unusual for her. She is eating well (EBF) when she wakes up to feed, and has given me a few smiles (and a few tears!) when she is awake, she just doesn't seem to be able to stay awake for very long. Should I be worried, or have other people experienced this?