How do I tell my Mom I need to see a doctor?

I'm so afraid to tell her I need to see a doctor about my compulsive overeating. It's out of control. I'm 16, and I'm just so afraid that she's going to pull an excuse for it or say "no it's normal for a teen" or "it's just because of your Celiac Disease" or blah blah blah. Should I just say I need to talk to my doctor about something and not tell her about what? Or tell the truth? I'm just scared that she's not going to believe my problem.. The only way I know is from reading a ton of stuff online. Should I show her the stuff I read? I'm desperate, I just want my life to return to normal so I can stop obsessing over my body and food.