Hi Kate

Thanks for sharing these images.  Unfortunately we are not doctors and cannot give you a diagnosis.

My first thought is that you really need a specialist for this...a dermatologist. 

Here are some questions for you in the meantime:

Are you taking any new medications?

Have you been exposed to any plants, animals, insects, new detergents or soaps?

Is your rash limited to your limbs? 

Do you have any other symptoms like fever or flu-like symptoms? 

Does anyone where you live have a similar rash?

Any possible way you have been exposed to ticks? 

Do you have any known food allergies?

Here are images of Lyme Disease.

Here are images of ringworm.

Here are images of eczema.

The only way you are going to figure out this mystery is to be seen by a dermatologist.  Keep a log of your symptoms and these photos.

Hope you find out what this is soon!  If you find out please let us know...you may help someone else in doing so.