pythons have indeterminate growth which means they never stop growing, however there growth rate will slow down dramatically once they reach a certain age...
I wouldn't try and over feed your snake to get it to grow, it will just lead to health issues, just enjoy your healthy snake at the size it is now and over time it will reach the size you want...
if you want a larger snake over night then it is probably better to just buy an adult
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also i think head size is relevant to the size of the food items your snake is eating, maybe try up the food size and feed him/her less oftern, but that just depends on what you are feeding him/her now