Hello again, It would be way more than exceedingly rare that any deliberate attempt to sedated you would be possible if you had a ventilation fan in the window. Thats the key point to remember.
Without a ventilation fan it would be possible to sedate you by introducing one or another of the various sedation gases used in medicine, or just carbon dioxide in a high enough volume. It is possible, but would generally require a good sized tank of gas that you would see outside of your house,
There is a chance that an improperly vented gas appliance in your home or even a neighbors home is leaking carbon MONoxide gas into your home, that is odorless but its associated gases are not odorless, You can buy a carbon MONoxide detector for less than $50 to detect that. Sleepyness is one side effect of carbon monoxide gas, it is very often lethal in heavier concentrations.
You may also want to buy a carbon DIoxide gas detector as well.. that is only lethal in very high concentrations, it is also odorless.
These detectors can be battery powered or wired into the house power, and are available at most larger hardware and home supply stores.
The house settling is another issue. Cracks in the walls and the increased space between the baseboards and the floor indicate settling... the width of the cracks is an accurate measure of the amount of settling.
You can contact a local medical supply store that caters to people who need wheel chairs and special beds.. they will also have the oxygen tanks and equipment that you are interested in for breathing at night.
The cheapest and most practical solution however is ventilation...
You can buy carbon dioxide detectors at the link below
Stay in touch as necessary, we can go from there.