One should not lose more than 10% of their body weight unintentionally over a short span of a few months. If so, it would be advisable for you to check with your doctor to screen for other organic diseases that might cause the loss of weight.
Stress by itself usually does not cause a loss of appetite resulting in weight loss. Try to manage the stress by keeping your maintaining a healthy lifestyle i.e. daily exercise for 30min, good sleep and hygiene, a well balanced and healthy diet, and avoiding smoking and alcohol. Relaxation methods such as meditation, spending time with friends and enjoying your hobbies are good ways to take your mind off the stress. If you have feelings of depression or constant worrying that affect your daily function, you should see your doctor.
Hope this is helpful.
