Unusual pain in my heels

I normally sit in my bed and pull my knees up and rest my laptop on my lap while doing work in the evenings but syrange things are developing. I have noticed within the last two months when I woul situp in bed and pull my knees up my heels have become very sore. It feels like blisters under the ball of my heel and very painful to the touch to the point I do not want to walk on them. I cannot sit up in my room to read a book because resting anything on my lap and pulling my knees up kills my heels. If I go a week without doing my work in the evenings the soreness goes away. I do not rub my heels in the bed they just sit still as I work. I have asked my Dr. but he did not understand what I was saying. I have also noticed that the pain has been moving down to the sides of my feet if I try to switch the posision when sitting. I need to find out what is goin on. I can hardly work and I am not over weight, I am in my early 30's. please help!!!