No offense... but if you're that old... why should it matter what your mom thinks? And if you're so worried about her finding out, why not go somewhere else? I used to have the same problem with my mom, she'd find things in my room while she was tidying (I hate cleaning my room so sometimes she ends up doing it) and flip out about it. I've grown enough to know (I'm actually younger than you lol) that it's a part of life, and parents will have to accept that one day their children will grow up and will start having sex. Of course if my mom knew what I was planning for my birthday... she might go into cardiac arrest lol.

But anyway, she needs to deal with it. You're a grown man now. Time to act like it =)