Why did my hair fall out again after it just grew back?

This needs an in-person evaluation. I suggest seeing a hair loss expert now to evaluate and go over your condition and provide you information about your best treatment options. There are great non-invasive options like prp/progesterone and/or hair transplantation. See an expert. Best, Dr. Emer

This requires a more in depth evaluation and up close exam. Telogen effluvium and it's various triggers need to be considered as does alopecia areata. See a dermatologist if things don't improve.

This is a difficult problem and the cause is most likely stress related, assuming that you are a female.  This rarely happens in men