I think I may have the same problem, but I don't think it could be you passing gas without knowing it. I did some research and google showed me leaky gut syndrome. Leaky gut syndrome is when you have a small puncture in your stomach and some undigested food, or your feces, can get through it and all the toxins have to get out by going through your blood and finally it excretes the toxins through your skin. That is why you may smell like feces. A treatment is to take L-glutamine a few times a day. This can close the hole or ulcer in your stomach and stop the undigested food from getting into your blood and may stop the smell after a while. I just started to try this and you should try it as well. You should do some research about leaky gut syndrome as well.