What kind of toxin am I exposed to?

Ok, I know it may sound like I'm crazy or paranoid or something. I can assure you I'm not. I have on and off been getting cigarette smoke into my apartment. When I complained to the neighbor it momentarily stopped but then I got something else. A friend who was up here said it smells kinda like burnt foam rubber. It doesn't really smell so much but I notice it when I come home.

I have complained again but to no avail. The neighbor just denies it. The symptom I first noticed after being exposed to it for a while was being out of breath after walking short distances. Later also rapid pressure over the lungs, heartbeat, dizziness, trouble walking straight and kinda foggy mind. I am certain it's caused by this since I got the first symptoms after I noticed this crap.

What I really wanna know is what it could be? It isn't ordinary cigarette smoke. It isn't carbonmonixid since an alarm I borrowed didn't register anything. Could he be burning some kind of plastic? What kind of gas/smoke fits the description and can cause these symptoms?

Again, I am bot imaging it. It really happens. Have some reasons I haven't contacted the landlord yet. I just want suggestions what it could be?