And you don't have to tell anyone if you don't want to. Some people feel that keeping their practice a secret is the best course of action, due to some reactions they fear will happen. But that doesn't mean you have to keep it a secret ;)
Being Wiccan is one thing, being a witch is a completely different thing. Folks have confused the two of them for a very long time and it will probably continue to be a thing.
That link will explain the differences sufficiently.
If you are interested in Wicca, I would read up what you can on it (the original tradition) and find a coven nearby you who follows that original tradition when you become 18 or 21 (covens differ on which one). If you are sill a minor and/or living at home, you're fairly stuck until you become of age and/or move out, as no one will take the legal risks of taking on a minor without parental permission, and sometimes even with it.
If you aren't looking for the original tradition, I wouldn't stick to calling it Wicca (because if it doesn't trace back to Gardner it's not). You can always follow your own path and be eclectic, most people are.
You don't even have to be a witch to perform some form of magic. I'm not a witch and I'm very proud of it.
Arisa, I do know that being Wiccan and being a witch are different things, I'm exploring Wicca to see if it's for me, but even if it isn't I will still be a witch.
That's all good. :) Just making sure that you know.
I would also be careful with how you bring it up to your mom. You know her, you know what will set her off. Try to do and say things that won't set her off and will actually put her into a good state of mind to listen.
So just saying "Hey, mom, I'm magical now, I need you to buy my some candles" Isn't a good idea? : P Kidding! My mom's not extremely devout, like I mentioned above, and she's a reasonable person, so I think she will understand.
As for Patron God, I look at the Christian God as being a single thing I call "The Source," as in the source of everything.
God and Goddess as Wiccans look at it, IMHO, are the masculine and feminine aspects of this source. Selene is obviously your connection to the feminine aspect of The Source/The Christian God. If you feel you need a specific Patron God, Meditate on that to reconcile your Christian upbringing with your current views. That's what I did, as well as incorporating Eastern philosophies into my Christian/Wiccan beliefs.
My masculine aspect/Patron God I feel connected to is Lugh, of Celtic belief, and my feminine aspect/Matron Goddess is The Morrigan, also of Celtic belief. Both, to me, comprise The Source, which equates to the Christian God, to me, anyway.
