Check your exhaust pipe. I found on most RV's the darn exhaust extends only inches past the edge of the side of the RV.:R
I wrote all my headaches off to various things. I tend to end up sleeping on my couch where the gen is. It was the exhaust fumes. Not enough to knock you out but as we all know you don't really have to smell it for it to be dangerous.
Here is what it looks like, if you are not familiar with the Gen-Turi.This picture also looks like the gen is located in the back like yours is.



I don't leave home without it.:C