Excessive stress often results into loss of sleep and appetite, sadness, frangibility, loss of stress etc. In your case you identified study pressure is the stress. I don't know what course you are perusing but usual problem are extensive course to cover, shortage of time, distraction/disturbance in study routine, loss of confidence, high expectation of other to perform well, inadequate support from near and dear etc. are underlying operating mechanism to mount stress.
some common tips to reduce stress are - Avoid unnecessary stress (Learn how to say “no”,Avoid people who stress you out ,Avoid hot-button topics,Pare down your to-do list), Adapt to the stressor (Adjust your standards and attitude,Focus on the positive),Accept the things you can’t change (Learn to forgive, share your feeling), Do make time for fun and relaxation (Connect with others,Do something you enjoy every day,Keep your sense of humor) and Adopt a healthy lifestyle (Exercise regularly,Eat a healthy diet,Reduce caffeine and sugar,Avoid alcohol, cigarettes, and drugs,Get enough sleep).

Some useful sleep related tips are- Sleep only when sleepy,If you can't fall asleep within 20 minutes, get up and do something boring until you feel sleepy,Don't take naps,Get up and go to bed the same time every day,Refrain from exercise at least 4 hours before bedtime,Only use your bed for sleeping,Stay away from caffeine, nicotine and alcohol at least 4-6 hours before bed,Make sure your bed and bedroom are quiet and comfortable.

If such method doesn't work that better to consult physician or mental health professional as medication and non-medication treatment re available for these problem.