Forgot to update this thread, which I hope can help someone in future because its taken a while to get this sorted out.

I've kept getting as much treatment as I can (osteo, chiro, acu), as I noticed I burnt my back with the hot water bottle, which I have pretty much had attached to me 24x7 - I saw in the mirror my back had red and purple blotches all over it even with no heat applied, which has now gone red/brown. The panadol osteo was doing nothing so I stopped that as well, don't want to load my body up with a drug that is doing nothing for it. But it's left me short of options.

Its definitely a thoracic spine issue, like Pholi mentioned, only it goes around the side of the ribs instead of down. I started getting a burning sensation around the front of my ribs, its a horrid stinging/burning sensation - it pulls when I turn over in bed, or just randomly flares up throughout the day and feels like sunburn to touch. I saw the chiro today who said it was 100% from intercostal nerve interference, have googled a bit and it seems to be called intercostal neuralgia, which can occur in pregnancy and often as the result of issues in the thoracic spine. So its all making sense. Apart from treatment to help get some relief, I have been ordered to cut out bending down (which puts more weight on the belly/skin) and sitting - I have tried to lie down when I can but its hard when you're a busy mamma. I have to keep reminding myself I am almost 38 weeks and I really have to get some rest, but you know how it is. I'll have to see how that goes getting more help around here from the kids lol but its nice to understand whats going on, and it all makes sense. Hope this helps someone in future... it seems a very vague and confusing problem (yet debilitating at times) with not much you can do about it.