I miss sleeping on my back... the reason for sleeping on your left side is that the main blood vessels to your heart are on your right so if you have your right side upwards then its easier for the blood to flow - thus less strain on your overworked body. I learned that at antenatal class!!

I found one of those long maternity pillows an absolute godsend - got one at 22 weeks I think and it so helped me sleep better...much better than the odd pillow. Lately though I started getting bad hip pains, and sleeping worse but I've found that putting a cushion under whichever foot is on top (does that make sense? if i lie on my left side, the cushion goes under my right foot) - that seems to help a lot with the hip pains - I think its cause its keeping my hip in a natural position - plus having your foot on cushions is good for sore ankles - which is why I started doing that in the first place.
I live in hope that one day I'll sleep for more than 2 hours at a time again!!