There are two type of stress which are physical and emotional stress. Physical stress  can be caused by traumasurgery, a car accident, or a severe illness.  Emotional stress can be caused by a divorce, death of a love ones, loss of a job, getting married, depression, increase in financial obligations, or caring for an aging parent just to name a few. Stress can take a toll on a person and can cause hair loss.  When you have a stressful event, it shocks the hair cycle causing the hair to go into telogen phase (fall out stage). The hair loss then becomes noticeable and can occur up to 3-6 months. 

I know your question is what can I do.  Well I have a few tips to help you prevent hair loss from stress.

-Your hair will grow back as your body recovers

-Talk with a therapy or dermatologist

-Exercise

-Find ways to relieve stress such as read a book, do breathing technique, take a walk in the park, listen to soothing music, or spend time with family

-Do weekly shampoo and conditioning treatment

-Eat a well balance diet

-Massage Scalp

-Take daily supplement

-Laugh

Hope this information helps and please feel free to comment below if you have experience hair loss due to stress or share ways you relieve stress.