What Causes Pain In Hip And Calf Muscles?

Im an athlete, so I work out every day. Im 5"7 and weigh 141. Most days I go on a long run and then do an abb workout. This past tues I had problems getting out of bed because I felt soo much pain in my butt. I was in so much pain, I couldnt do my workout. The next day I attempted to go running, but i was in too much pain. I decided to get on the eliptical machine instead. When I get up or try sitting down It hurts alot. Today when I woke up the back of my left calf was hurting and its hard to walk on. Im a student athlete at George Mason University, so I am used to hard core working out. I dont understand what is happening to me right now.