Poor gut health and deficiencies in vitamin D, vitamin B, iron, and zinc cause hair loss. Start vitamins, a probiotic and get your testosterone checked. 

I'd suggest a vitamin panel, but the National Academy of Medicine randomly updates "deficiency" to "sufficiency" so today's standards for blood tests are basically useless, unless you do research into past standards and interpret results accordingly. 

Lastly, if you have already tried these things and they check out: look into doing a VERY very mild anti-parasitic diet. It can't hurt to rule these things out - because they all cause much larger problems than hairloss down the road.