Please get a diagnosis from a dermatologist. You may be having a condition called alopecia areata, if there are well defined patches of hair loss. Other diagnosis may also be possible and can be ascertained while consulting. However, this is the diagnosis most of the times. Treatment is simple and has different approaches. You need to discuss with a dermatologist to understand it at length. Refer to the link below for more information on the subject. https://www.aad.org/public/diseases/hair-and-scalp-problems/alopecia-areata