How To Treat Thinning Of Hair Receeding At The Temples?

hi, i am worried because i am 15 (october 94) and my hairline has been receeding at the temples over the last 5 or so months, i have grown my hair so its kind of covered up but its at a stage now where i would rather not spike it up for school, as not to risk people noticing.
my diet isnt great, but not terrible, i dont eat much fruit though.
my dad and grandad have thin heads of hair but not at my age.
i use hair products to style my hair as it is naturally very straight

please help, just some reassurance would be nice, im in constant worry and i cant study right at the moment