Get some rest
The fatigue you feel in the first few months is due to high levels of pregnancy hormones circulating in your body. Later on, it's your body's way of telling you to slow down.
If you can't sleep at night, try to take a quick nap in the middle of the day to catch up. If that's impossible, at least put your feet up and try to relax for 30 minutes.
If backache is disturbing your sleep, try lying on your left-hand side with your knees bent. Placing a wedge-shaped pillow under your bump may help ease the strain on your back.
Exercise may also give you some relief from backache. It can help with sleep problems, too, as long as you don't exercise too close to bedtime.