The best thing you can do is just try to relax and accept that if you can't sleep, you can at least rest. I found that I'd get wound up because I'd be sleeping terribly and knew I needed to sleep better to get through the next day of work, but in the end it was like trying to fight with myself

not the most successful strategy really!
Try having a chamomile tea and perhaps a warm bath before bed to get yourself into a drowsy state. If your lack of sleep is in part because of backache... when dh has given me a massage before bed it has done wonders for my sleep!
That and finding the right balance of pillows. Putting a wheatie bag along my back and/or under my bump also helped (and still helps!) me to relax faster in bed. I was surprised what a difference this made, especially as my bump has been considered quite compact all along.
The other thing is to avoid the stimulation of tv or computer before heading to bed (something I found little more difficult...)
If you wake in the middle of the night and find yourself tossing and turning, get up and have a hot drink and some toast or something. You'll probably find it easier to relax again when you head back to bed.
Anyway... I hear your pain!!! Hopefully some of these ideas work for you as well as they have for me. But remember, when all else fails, try to relax so that even if you can't sleep you're at least letting your body rest. Sometimes that's all we can do!