What Causes Red Spots On The Legs With Pain In The Back And Throat?

Hello, three years ago I got dark red spots on my legs, on the lower part of legs were bigger and higher were smaller and without profile. Doctors said it was just a reaction on some medication that I took against flu. One month ago these spots repeated, escorted with pain in my throat and lower-back part. I got antibiotics and it cured, yesterday everything started all over again, same simptoms. Could this be kidney infection or what? Please help...