Reddit reviews Adhesive Wall Hooks

This is just a few seconds of searching from a random internet stranger, but look for a few of these at your local wal-mart. Also, I always thought that CO was heavier than air, but apparently it is slightly lighter than air. This suggests that CO detectors should be placed rather high, on the ceiling if possible. If you're in doubt, just place one as high as possible - if you get a reading, use an extension cord as a temporary way of measuring the levels in different locations, high or low. (I'm not sure how quickly the sensors update, you may need to rig a way to hold the sensor in place for a few minutes, try these things.)

Best of luck to you and your friend! (Maybe get a detector for her as well... though it sounds like you're more affected than she is.)

Also, keep an eye out for /u/RBradbury1920, he left post-it notes for himself, it turned out to be a side effect of Carbon Monoxide poisoning. (Only 100 PPM, apparently.)

Edit: How close do you and your friend live? There might be something in the environment doing this to both of you, such as a gas leak or something. But if so, then other people might be noticing strange things as well....