Hello Friend, thanks for reaching out here for help. It may be due to stressed study schedule for your exams. Relax a bit. Give gaps in your schedule. Try some hobbies to relax. Reduce the use of mobile or internet. If you feel it may not be the reason, then you to provide more details for further evaluation.
Health Tips
Have proper rest and sleep. Have a cup of warm milk before sleep. Try meditation and yoga for stress relief.