As oxford mushroom already stated, there are more causes for
hair loss.
First I thought of the hair loss typical for you men, due to your
hormones, but you said it's not really symetrical so now I am not
sure about the hormones being the main reason.
If you started to use a new shampoo which you never used before,
this too can be a reason, your hair, follicles or head skin can be
sensitive on one or more of its substances.
I think you should see a doc, and also avoid stress (this too can
hairloss), have a balanced diet rich on selenium, zinc and biotine
(vitamine H).