Don't Worry, Be Happy...

So in light of Abby's recent milestones concerning her bottle and her booty scooting, I've been thinking about other milestones. I think like many new moms, I worry when I see that other kids her age are doing more things than she is. This morning (when I was up at 5 am for absolutely no reason), I was thinking about her current state. Most of the books say that 4 month olds should be giggling quite a lot. While Abby definitely giggles (sometimes even howls when being entertained by her new BFF Betsy), she doesn't do it very often. Does that mean I have an unhappy baby on my hands? She smiles lots and lots but it usually takes her Daddy's tummy "raspberries" to make her really get going and sometimes, even that doesn't work. Every single book, website and blog about babies tells you that all babies are different and will hit milestones at a different pace. But is happiness really a milestone? I don't think it is, so I now I am concerned that Abby is unhappy. Not sure how to fix it either.