hair getting thinner

I’ve noticed that the longer my hair gets the thinner it seems to get as well. It’s currently about mid butt length and my goal is to eventually grow it past my butt but I’m afraid it will be too thin to look good at that length. Looking for advice to help maintain its current thickness or potentially regain thickness! For reference I am an adult female with 1a to 1b hair. I wash once every 7-14 days, use low heat maybe once a month, oil the ends with Moroccan oil every other day (or everyday if needed), sleep with my hair in a loose braid with a loose cotton hair tie and a silk bonnet silk pillowcase combo.