If you have been having sex since you were 12 theres a good chance that at somepoint you haven't been responsible about it. If your mom is the type that will understand, which at 16, she should, then yes tell her. Maybe not about how long you have been having sex, lessen the blow to her!! But why not tell her just that your having sex now. Are you on birth control?????? Only a doctor can give it to you and your mother probably gets the bill since your a minor. This way you can get tested, and get on birth control to avoid situations that -trust me- you don't want to be in. I got pregnant when i was 17. And std's. Your life is more important then telling your mom something. hiv aids?? On the other hand if your family is a little different, strict, like gonna kick you out for this stuff, there are other options. Planned Parenthood will accept you as a pateint, knowing that you don't want your parents to know. They base your fee on how much you earn, which if your 16 probably not much so the cost will be very very low. They don't send things to your address, if they have to call or something they will even act like a freind from school!! I think it depends on the state you live in, but at 16 you have the right to your own body in the eyes of the law. No matter what you do with your mom, be safe first. Theres no problem with having sex, but keep yourself safe above anything else!!