METHYLPREDNISOLONE 4mg 21 tab

This is my first day taking this medication for itchy rash over most of my body. I am concerned as suddenly I feel pain in both of my legs. is this a side effect. My other medications currently are Vicodin for pain, zoloft for depression, atavan for anxiety, a prescription for acid reflux, a coated asprin a day. I also take daily calcium supplement.