I think i stress a lot maybe that's the reason i lose weight , but i am not sure.. i weigh 52 kg and i am 20 year old male. is there anything i can do?

See your doctor: Problems like these can only be correctly handled by your doctor in person. He/she needs to listen to you, perform an examination and possibly run labs or other tests. That's the only way he/she can find out what's going on and what to do about it.

Thanks for asking: The fact that you are asking the question indicates that you are being appropriate and are prepared to manage the issue. First would be good health habits. Eat healthy foods and avoid excessive carbohydrates. Sleep well without using alcohol or high dose drugs. Exercise in appropriate moderation. Have a fun hobby and find time for fun. Love someone thoroughly, including yourself.