My guess would be a viral rash. I think it’s a good idea to be prudent and check everything. But at some point in time, you’ve checked what needs to be checked and it’s time to observe. If it is something bad, it will declare itself. But most of the time, asymptomatic rashes, even petechiae, are related to mild viral illnesses.

Hopefully that’s all it is and it just clears. The month part is probably the most annoying/troubling aspect and I understand the angst. A second opinion sounds like a good idea.

Wish I could be of more help