Frequent stools symptoms and conditions

Have been taking Vytorin for about two months. So far, main side effects have been frequent stools, gas, and occasional diarrhea. Some tiredness; hard to know if it's caused by the Vytorin, though.

The only truly bad problems I've experienced happened when I ate a half a grapefruit. That night I awoke with a splitting headache and chills/sweats. The next day I had to take Pepto Bismol before leaving the house because I was constantly in the bathroom. Obviously the grapefruit doubled the effect of the medication.

Dark, tarry frequent stools which is of great concern. I will contact my doctor immediately about this. Only been taking it for 2 days! Started with prevacid for 2 months which caused diarrhea. acifex was offered to me as a substitute that has "fewer side effects".