Also looks like tinea versicolor:

http://www.skinsight.com/adult/tineaVersicolor.htm

Click on the 4th picture (second picture down in the right vertical row... looks like yours.

While we cannot diagnose on the net, tinea versicolor does have tests for it.

It is pretty harmless. I had it on my forearms last year. It is fading finally after alot of treatment with an antifungal solution.

On very white skin it is pink and spotty like you have and if you get exposed to sunlight it will darken into tan patches. In darker skinned people, it turns the skin LIGHTER where infected.
It can occur in summer when you perspire more, etc.

I don't know why I had it on my forearms...but that's life!
It does not itch or burn. But I did get mine after a skin reaction from something in the water on vacation. I blistered for about a week, and when that healed, then I had the tinea. why.
The current theory which I called a professor at a university (thinking it was the zebra mussels spawning), and he said it was a photosensitive dermatitis from the algae bloom in the cold water. I only get my reaction during the last week of June and first week of July typically. Other times the water does not react on me. Just this once it turned into tinea versicolor!

If I were hot etc...it would get redder. Then when cool, you can barely see it.

Your rash does not look like scabies. Scabies reactions are much redder and itch so there are scratch marks left on the skin as well. Tinea Versicolor often comes in young people. Adolescents, and young adults. You can Google it to find other
pictures. The patches can be small or merge together ...sort of like a map.

This is just my opinion. The rest of your symptoms do not match to Tinea versicolor. There should not be pain, or any itching.

A viral exanthem is typically redder than your rash. But it does fade lighter and lighter eventually. Also the viral exanthem is not raised like yours is. Yours does resemble a contact dermatitis also. That will not show positive to the KOH test for tinea. People can react to soap residues in clothing (from improper rinsing) or from fabric softeners.
There could have been chemicals on the old mattress and who knows
"what else!"