What Causes Fatigue, Increased Appetite, Drowsiness And Pain In Calf Muscles?

Hi, I am a 21 year old IIT student. I need to ask you a certain amount of questions about the change in my health I am undergoing.Till last December I was very hard working and used to work almost all through out the day physically and mentally, taking up very challenging jobs. But since this semester from January I am feeling a little exhausted. I have started to feel much more hungry my diet has increased by two times. I feel very sleepy and sleep for almost 12 hours a day.My calf muscles experience a lot of painful while I am about to sleep. Even if climb two floors I start having breathing problems?Could you let me know the reason for these sudden changes?