If i tell my doc i am not sexually active even though i am (because i am 16 and don't want my mom to know), what is the worst that could possibly happ?

Your doctor ; you: For your best health, you and your doctor need to be on the same page. If you don't tell the truth, your doctor won't know all the risks you need to be covered for, such as being tested for std's. Ask for some time alone with the doctor so you can speak frankly. At 16, this is reasonable and your mother should understand.

Honesty is best!: Your doc will not be able to help you make the best decisions. He/she may not be able to accurately diagnose any problems you have or give you the best advice and treatment. Your doc can give you the advice your need and he/she doesn't have to tell your mom.

Sterility: If you are sexually active you should be screened every 6 months for STD's.Since at least two of these can remain relatively free of symptoms while they quietly destroy your ability to have babies, you might want to reconsider. If you pick up a symptomatic STD the cause will be obvious, but proper treatment may be delayed if you are not honest.