HOW DO PEOPLE KEEP FINDING MY SECRET INSTAGRAM???

It doesn't have my full name, it doesn't have my picture, it's private, it's not connected to my main account or anyone I know. Ok, I decided not to block my best friend when she requested to follow, but the people I know who are requesting to follow me wouldn't be connected to her. The profile picture is a drawing I haven't shown anyone! How do they find me?