I need help! Please help!

I've had my period for full year one week every month BUT my mom doesn't know. She's now talking about taking me to a doctor for it . I haven't told her Ive had my period because she makes it so weird! Like she try's to be my best friend and she's a huge bitch to me . We don't have a close relationship but when I told her when I had my first period she made a huge deal about it and then I told her I haven't had one since. How do I tell her I started it ? Please help me !!