Are you suffering with depressive disorder ? If not then I am not in favor of leave and that also for 3 weeks. Sometime people develope phobia at work place due to adverse work situation and doesnt want to work in such situation. If you are bored with your monotonous life then take break for 1 or 2 weeks, spend sometime with your family member and plan a pleasure trip with them for some beautiful place and again join your duty. If you think you are unable to work in such situation start seeing some another job and leave the place.
Next Steps
Dont try to escape even in mild stress.you are only 18. try to face it . otherwise escaping tendency will become your habit.
Health Tips
Go for yoga , meditation, relaxation exercise and balanced nutritious diet.