I found with sleeping, that a pregnancy/body pillow helped SO much with sleeping even before I got a belly! It just meant I could sleep on my side comfortably and feel supported!!! HIGHLY recommend getting one!
I had a long, full body straight one so I could drape myself over it, i know you can get round ones n stuff but I loved mine! Got it from Pillow Talk for like $30!!

Aqua aerobics is a great idea!!! Prenatal yoga is awesome too!! I found it so relaxing and the stretches were gentle and great!