i've never had loss of hair due to hair straightening

if you are uncertain about the product that your hairdresser used, then it might be a good idea to ask them what it was they applied on your hair. though i don't think that this is the reason for your hair loss. they might have only applied a serum to your hair which is common practice.

is it possible that you are using a shampoo that isn't agreeing with you? or maybe you're going through some kind of stress? and not consuming the right foods for encouraged hair growth?