What is this rash?! (With pics)

[Runningupthathill82]

Can anyone help?!
Before I try the farce that is getting a doctor's appointment, I was wondering if anyone had any clues what this rash could be.
I started out with a couple of spots a few days ago and now my entire back is covered. There's a few on my tummy too.
It's not particularly itchy and I'm not feeling ill, just a bit run down and snotty.
Any ideas?

I can't tell from the picture, are they flat or blistered? If they're blistering, I'd say chicken pox but I'd expect them to be itchy!

Slightly raised, but not blistering.
I don't think it's chicken pox - I had it as a child and didn't catch it when the children had it, so I reckon I'm immune?
Thank you though! It's a mystery...

It may be pityriasis rosea. If it is that it can last for a number of weeks, its not harmful to you however.