I feel your pain Lisa, i had it so badly in pregnancy #2 that i would wake all through the night and my hands/arms were so numb i would have to get up and wack them on the mattress to get the feeling back. I was given these elasticated things sort of like gloves without hands which are supposed to keep your hands straight when you sleep, but they didn't help at all (this was from the physio). Unfortunately the only thing which helped was giving birth! it totally stopped that day.

I would consider trying an osteopath though, i've since been seeing one for a few months for neck problems and have had great results. Helped with my baby's reflux too, so may be worth a try.