you're overworked, and very stressed. You're probably also malnourished due to dietary decisions consisting of little more than "What's in the vending machine?" or "Where's the closest fast food joint?". If so, there's a high likelihood that your Liver and Gallbladder are both causing you problems. Depression is a common symptom of Liver issues. Add in a poor diet with high cholesterol, and your Gallbladder and liver a probably full of gallstones. increase your Ginger and Turmeric intake (to increase bile flow/digestion) for a few weeks, and spend a weekend doing a Liver Cleanse/Flush to remove the stones already in your system. I'll bet this helps you more than you'll ever realize.

Good luck in your studies.