Wavy and Puffy to Straight Theory

i was just thinking back to when i was younger. i had really straight hair, but then somehow it got wavy, puffy and a bit curly. i thought that it was because it ddnt comb my hair for like a whole year in my last year of primary school, but somehow i doubt it.

anyway i was wondering if it would be possible for me to somehow get my straight hair back again and i thought of shampoo. now from what ive heard if people stop using shampoo for like more than a week their hair becomes oily and aint that why hair becomes wavy and puffy: because there is not enough oil in the hair? so if i wash my hair every night and it becomes really dry then surely my hairs oil production will go sky high, because its trying to balance out the dryness, and my hair will get its oil needs and eventually become straight again after some time?

just a thought, dont think that it would work but man am i desperate to have naturally straight hair again like the good ol days :P