Sure, I'll be happy to explain to you why you're on birth control, but still not allowed to have sex. It's an old saying from like Season 2 (or maybe it was Season 1) of Stargate SG-1: "The very young do not always do as they're told." The Nox said that; they kick ass. Well, they obviously don't kick enough ass to not be ageist fuckers, cuz then they'd know that the very old, very middle aged, and very everything else don't always do as they're told. However, this trait is most noticeable among young people (because that's where adults notice it the most, not because that's where it happens the most).
All that long drawn out bullshit for a very simple answer. You're not allowed to have sex at all, but your mother knows that you might disobey that order, because you're young and that's what young people do. Birth control is the fallback plan in the event that you don't act like a
Get the picture? Parents know that eventually their control will weaken and their kid might do something nightmarishly horrible like engaging in the single most natural and pleasurable act of which human beings are capable. OH THE HORROR!
Sarcasm aside, sex can also be one of the most dangerous acts human beings can engage in, which is why parents tend to fear it. Now, the intelligent course would be to educate one's children against the dangers so that you don't have anything to fear should they have sex, but a great many people are simply not that intelligent. My point is, I hope that YOU are educated and not taking stupid risks. Use a condom - every fucking time! - regardless of whether you're on the pill or not. If you're not practicing safe sex, then you're proving that you're just as fucking stupid as your mom apparently thinks you are.
Now that the obligatory (but very fucking serious) warning is out of the way, let's address the question you didn't actually ask, but the main problem you're having. You wanna keep greasing your guy's pole, but you're 17 and mom says "DANGER WILL ROBINSON! KEEP OUT!" So, how do you continue to fuck him against her wishes... that IS what you really wanted to know.
The responsible answer is that you should obey your dear mother's wishes because she loves you and only has your best interests at heart. Also, you're far too young to know what you really want, etc, etc, blah blah blah.
Now, see, that was the responsible answer. Funny, wasn't it? I, however, am an irresponsible asshole, so here's the correct answer. As long as you are over the Age of Consent in your state and your boyfriend is too, your mom can shove her objections straight up her fucking grilled-cheese cunt! Or, if both you and your boyfriend are under the Age of Consent, then you may .
Ok, in all seriousness, what the fuck do you need me for? Parents have been telling their daughters "NO DICK GOES THERE!" for centuries and for all of those centuries teenage girls have been saying "Yes, mom, I understand" and then sneaking out the fucking bedroom window to have a doggy style session with Johnny Hotstuff in the back of his pickup truck. My advice to you is simple: Don't break tradition! Lie to your fucking mom and do whatever the goddamn hell you want to do behind her back! I did it when I was a teenager and, guess what, so did your fucking mom and so will your kids. It's a proud tradition and who the fuck are you to question it?!
All joking aside though, I absolutely mean the shit about safe sex. You're an idiot if you don't slap a rubber on his pimply pecker. This is my best and #1 advice to you. If you don't listen and end up sending me "Dear Galen, I have the herps now" I will post it on the front page and laugh at your stupid ass because you will have gotten what you deserve for not fucking listening to me!
Have fun with your guy and don't get caught (by either your mom or the crotch rot). If you do get caught and your mom is now reading this... Hi mom, I was only kidding. Don't blame me because your daughter's too stupid to take a fucking joke!
Wishing for your eternal damnation,