I agree with the previous poster regarding flaxseeds. They do promote regular BM's, and are a great source of Omega 6 oils.
I also have a sauna, and I haven't experienced anything as you describe. The sauna will help you eliminate the mercury with the benefit of bypassing the internal organs to do so. Also weight loss is another benefit of the sauna, so I don't see that as your weight problem.
Suggestions: Water fasting, or colonics to clear any bowel blockage.
Good luck
Either the sauna or a Colon Cleanse (which I doubt it was the colon cleanse) caused me to have trouble digesting animal proteins.
It wasn't the sauna. If the Colon cleanse contained Psyllium, or Bentonite clay They both swell in the intestine. If you don't drink enough water with Psyllium, it will turn to a concrete like substance and block the bowls. The sauna requires a lot of water as you are sweating water, so doing them at the same time probably wasn't a good idea.