I don't have an answer for you but, I have the same problem in my apartment.
No one seem to know what the problem is. And there's only a select few who can smell the toxins that are making us sick. We cannot enter the bedroom without
wearing a mask & goggles. Hope you find the source. If I open the window when
its really cold out, I don't smell the toxins. Once its closed up the toxic smell is still
air born in there somewhere. Good luck on finding your problem.
Dee