What Causes Red Spots On The Lower Back?

I woke up today and have red spots on my right lower back. They are not raised or itchy. It is about a 2 or 3" squared shaped pattern of little marks...almost like I was pushed up against a mesh chair (which I wasn't). I am taking clomid and just ovulated...won't be able to check for pregnancy for another 10 days. I am 39, 5'5", 177lbs. I do have sensitive skin and can get reactions to foods or tanning agents, but I haven't had anything different other than some watermelon yesterday, which I have eaten occasionally throughout my life.