I bet your baby is fine...Teagan loves water and has recently started drinking a lot (or maybe she always has been and I've just noticed it). I took her to the vet last week for something unrelated and mentioned it; the vet didn't think it was anything to worry about. He said she was young (6 years) and doesn't exhibit any other symptoms, so he didn't feel she needed a test. She isn't peeing like crazy and her diet hasn't changed or anything. He said certain rawhides or treats or what-have-you can make her thirsty. I know that when I used to give her Greenies (I KNOW! NOT ANYMORE!), she drank LOTS on those occasions.
I really think she just likes water, especially if I have a glass or I put down a fresh bowl. I give her new water 4 - 6 times a day. It's filtered and my roommate thinks I'm nuts, but I don't like stale water and I'm sure she doesn't either!
I'm a little embarrassed to admit this, but our bedtime ritual includes me bringing a little saucer of water to Teagan while she sits on my bed before lights out - she gets one more drink before going to sleep!