Hi, last week I started taking Minocylcline(54 mg per day) for my acne . Since then, I ve had constant headaches (but I think I m prone to head aches), but what s concerning me is my stool . It s lighter than usual-a grayish green color, pebbly, and hard as a rock. There is also some undigested food in it and maybe a tiny bit of blood . Is that the medicine or something else? Could I drink more water or something to avoid this problem or is the only thing to do is stop taking it? Thanks