Attempting suicide

I was having a random conversation with a woman at work the other day, and for some reason it came out that I sleep with the blankets pulled all the way over my head. She just stared at me and asked "All the way over your head? You're face is completely under the covers?" People who know this about me always want to know how I can breathe. Since I haven't ever had a hard time breathing with the blankets over my head, I tell them that I don't know, but obviously I can. This woman made that standard inquiry, and then took it a step farther and told me that she thinks I might be poisoning myself by breathing in my own carbon dioxide. She wanted to know if I woke up at night breathing heavily...which I do not. She became more convinced of that I'm in danger the longer this was discussed, until at some point she told me that I'm probably killing myself off slowly by not getting enough oxygen at night. She even went so far as to tell me that I'm in peril of brain damage from carbon dioxide poisoning, and that the reason I sleep well with the blankets over my head is because I'm essentially drugging myself. I know most people think it's kind of a weird habit, but she's the first person to ever suggest that I'm killing myself. Who knows, maybe it's a good thing I don't get enough sleep afterall.