how to bring this up during appointment

f14, i have a doctors appointment coming up soon (just a check up) and im scared the doctor will bring up something in front of my mom that i dont want her to know. i’ve been struggling with eating for a little bit now and i feel like im only getting worse mentally and physically. i haven’t lost much, 15lbs since january but ive been fluctuating a lot. even though i haven’t lost much i think its started to effect my overall health and im scared he’ll notice and bring it up in front of my mom. what are some ways i could bring it up to him privately first without my mom being around?