What would cause a skin rash? it does not itch, but is spreading. i don't recall using any new soaps, lotions, detergents, medicines, etc.

Too many things: Too many possibilities to answer here in such short space. As you said, you haven't had any contact with things that could be a cause so you should get the rash looked at by your doctor.

Many things: Rashes can be caused by many different types of things such as exposure or illness. In order to determine what is causing your rash you need to be seen by a doctor. Rashes need to be seen in order to try to diagnose and treat them effectively.