What's this bad flavor I'm experiencing...

On almost all mild cigars and some medium, I pick up a sickening flavor once I am about 2/3 through the stick. The cigar will taste fine up until this point. It was most prevalent in a RP Connecticut I had a few nights ago, but it's also been present in an El Mayor Emerald, Gurkha Symphony, and CAO Gold. I wouldn't describe it as bitterness, but it makes me nauseous. I've had cigars make me feel sick/light headed, but that was due to my inexperience and not the flavor of the cigar.

I might try smoking another mild cigar tonight so I can explain the flavor better.

Any ideas?

Thanks,

Wyatt