Your body does not heal because you are not absorbing nutrients in your intestines needed for your body to heal, for whatever reasons. It is one of the most common symptoms of damaged villi, the little hair like structures that line the intestines that absorb nutrients. Poor dental health, depression, IBS, all symptoms of malnoutrition or absorbtion problems. I think it's a lack of vitamin K that causes buising and skin discoloration, not assocaited with a normal scar, pink raised keloid type scars that fade with time. But you'd have to check with your Doctor for sure.
I really suggest you see a gastro specialist. You have something going on that may or may not be related to ME. You should be tested for a wheat/gluten allergy. It would explain a lot.
Vitamin, commercial isolated vitamons won't do anythign for you because they are not complete. A whole food vitamin, greenfood or super food would be better and most likely not upset your stomach if you mix it with food or fruit smoothie. But you should still see a Doctor.