Oh man, so much. I lived with three other girls, all of whom are amazing and some of my best friends, but if I didn't make it really clear that I wanted to be absolutely left alone, they would just come into my room whenever and start talking to me. I felt so bad freaking out at them for it, too, because I didn't understand why I couldn't deal with them popping in to ask me questions like "What do you want for dinner?".
It happens at home, too. My parents especially will shoo me out of my bedroom if they think I've holed up for too long, and it makes me crazy. Sometimes, I can deal with people really well, even though they make me a bit hyperactive, but sometimes I just need to be the only person on the planet. Any sound of people nearby, even wwalking outside in the street, makes me want to scream. Which I've always found really odd, since I'm fine with having music on, usually, or even playing an instrument during my alone time. It's just sounds I'm not controlling that get me, I guess. Maybe a good pair of noise-cancelling headphones would be a good idea.