I have a sharp pain in my rib cage for two days. It's on my left lower side of thorax, on my back and lateral side of the rib cage, occupying an area as large as my whole palm. It started as a much smaller area but has been increasing ever since. I'm a 22 year-old female, with slightly low body weight. I first realized the sharpness of the pain while doing a mild exercise. I was lying on my left side and lifting my right leg but I guess I was feeling a softer range of pain before exercising. I have had the same exercising schedule for 2 years and I was not trying anything new or harder than I always do. Now my pain has been increasing for two days. I can't even breath without controlling my chest movements. My pain relieves while exercising mildly but I feel terrible while sitting or lying without moving. The pain is like I'm being stabbed. I was afraid of pneumothorax but I don't think I heard a tympanic sound during percussion. My trachea looks symmetrical. The pain feels both muscular and bone originated. I can't quite discriminate the source.