I'm experiencing penis shrinkage for 3 days now, my penis doesn't come hard again, is out of blood just small and stiff. i can urinate but i lack sexual urge, even if i try to initiate it, it just doesn't work, which drug do i take to feel better??

No drug - focus your energy on what you are suposed to be doing with your life, study or work, and try reading a chapter from the good book every day. yiu will find that as the days go by all ths concern will naturally disappear, I am sure!

It is not feasible to provide a meaningful opinion without taking additional history, physical examination and may be some tests. It would be prudent to see your doctor and discuss if you may be depressed. Counter-intuitive as it may seem, exercise may help. Start with low intensity exercise such as walking and gradually increase the intensity as tolerated. Drink more water. Wish you good health!