I had strep and possibly mono 1mth ago shortly i developed what looked like heat rash, rash came wherever i scratched. what could it be??? i have pics

Many causes: Depends on a lot of factors, including whether you took antibiotics. Mono itself can cause a sandpapery rash. Also being treated with Amoxicillin when you have mono commonly leads to a rash. Strep can lead to rashes directly (e.g. guttate psoriasis), or later on via scarlet fever (which isn't common in adults in the US). Also any time you get a fever, it's possible to get heat rash.