If you have noticed testicle shrinkage, accompanied by pain or discomfort, you should be examined by your family doctor soon. Otherwise, the testicle shrinkage might be due to something called cremasteric reflex, which is a natural reflex caused by the cremaster muscle. Basically it causes the scrotum and testicles to move upward, which resembles shrinkage due to the involuntary muscle contraction. During puberty (your age group) the reflex can be overactive, but nothing to worry about unless it causes pain. As far as reversing testicle shrinkage that is permanent, you would have to seek advice from your doctor about that.
Your at an age where you need to be sleeping between 8.5 and 9 hours, in order to be healthy and function well during the day. Sleep is very important, because when you sleep your body produces a growth hormone that helps your body heal from injuries and it increases body growth during your adolescence/ teen years.
It sounds like you may need to start a routine for getting to bed earlier, so that you can get enough sleep. Try this: make sure your last meal & last exercise is finished at least 2 hours before you sleep; stay off all electronics an hour before you intend to sleep, take a hot bath or shower to help relax before bed. Another natural sleep aid would be drinking a glass of milk before bed. You might want to ask your parents about taking low dosage Melatonin an hour before bed; it naturally promotes restful sleep. You can research Melatonin online with your parents, to get an idea of what it has to offer as a sleep aid.