Fear that she'll flip out and ground me

Well you can go on the birth pill in your local sexual health clinic and they will not tell your parents if that is really not what you want but they will only give you the birth pill if your going to keep on having sex.

I think you should tell your mum she may get angry and she may ground you but the thing is at least she knows the truth that way . Maybe you should sit her down and tell her you wanted to tell her because you dont like keeping things from her your sorry then say what has happened .xx

just tell her that you have realy heavy and painfull periods tats what I told mine ;) Xoxo

well id say you could either open up with your mum and tell her what you have been doing, well genrally tell her you dont have to tell her about the sneaking out but just tell her about having sex and that you have been using condoms (I assume you have) and now you want to go on the pill so your extra safe. She should after getting over her initial shock and anger respect that you have told her and that you want to be safe. This is the option I would choose as lies always come out in the end beleive me! The other option is to somehow arrange to visit your doctor without your mother knowing, or give her a fake reason and ask for them. The doctor by law cannot tell your mum that you have them. Also you could try asking a close family member or adult friend to help you get them without your mum knowing.

hope it helps :)