Throwing up & Rash

I have a 7yr old son who has been throwing up off & on since Wed., 3/5. He had a rash for a few hours on his arms Tuesday but by the time we got to the doctor's office it was gone. It came back today for a while and it was on arms, face & legs. No fever and he has had diarhea (diarrhea) since Wed., 3/5. He came home from school a few hours eerly Monday, 3/3 with a headache. The headache was there Tuesday morning but he hasn't complained of one since. He's very upset with me for having him on a bland diet because of the throwing up & diarhea (diarrhea). He feels fine in between the bouts.

[GirlB300]

The throwing up stopped so I think it's unrelated.  I thought I figured out where the rash was coming from.  He started using a new soap but he stopped days ago and it's getting worse. It changes areas rapidly through out the day. It's warm to the touch. He said he doesn't feel it. It's all over his body. I'm going to call the doctor back in the morning and take him back in. I've taken some pictures, one of which I posted on here. He's been playing in the mud in our back yard a lot but so have my other two boys and they don't have a rash. Can anyone help?!

[GirlB300]

It's fifth disease, harmless, praise God!