Question re: Constipation

I'm stumped and hoping someone can help explain this to me. I've been taking 50mg of Iodoral with all the accompanying supplements (incl. salt pushes on occasion, as needed) for the last couple of weeks, and have been having problems with constipation. Well, it's not completely constipating...but just a small amount of looseness and definitely not a complete emptying out! Twice now I've taken a break for a day or two and I go back to normal...2 good, solid BMs a day. What makes this even stranger to me is that usually the amount of magnesium I am taking alone is enough to flush me out but good! I've done PLENTY of colon cleanses, and have no problems with doing enemas...but would like to understand why this would be happening. BTW...I'm not doing the IP6...saving that for later.

Any insight would be appreciated...thanks.