I used to do the same thing,so i will suggest you can also try these methods if you are not able to memorize the formulas.

(1) Write all the formulas on a piece of papers and paste these papers on the door or on the wall above your bed or on the wall in you bathroom, basically places where you spend most of your time, and just read these formulas as many times as possible, this will help you in memorizing the formulas.

(2) Write formulas while solving the questions, write it as many times as you solve a question, writing these formulas while solving the questions won’t take too much of your time, but it will help you memorizing the formulas with ease.

Hope this will help you.