Dude, your mom knew, already. She was being politic and helping you save face, but, and I say this with the full retrospection of a 36-year-old man with kids on their way up, she *knows* how much you're shaking the turtle, and she **doesn't care**.
That's not to say you shouldn't keep it on the DL, right? Maybe pick up a little more (it stinks. If you're caching that much come in your room, people know), close your door, etc., but any parent of a 16-yo boy who thinks *their* precious little angel isn't blowing the pope's nose on a regular basis is a deluded individual.
So, be thankful that your mother was kind enough to save your slovenly ass as much embarrassment as possible by code-wording it, maybe make it a habit of wanking in the shower instead of your room (or at least take out the trash occasionally), and move on.