B12 makes me feel exhausted after 5 days

B12 should be making you feel more alive instead of how you are feeling i think the IBS and Fibromyalgia, are making this hard for the b12 action to inprove your system, even though this and i think iam right , the pain and diarrhea , are making you feel worn out , if you can get a med to help this, you might have an improvement have your doctor make a diet change , and a med change, improve your b12 exceptment, Medications are an important part of relieving symptoms. Your doctor may suggest fiber supplements or laxatives for constipation or medicines to decrease diarrhea, such as Lomotil or loperamide (Imodium). An antispasmodic is commonly prescribed, which helps to control colon muscle spasms and reduce abdominal pain. Antidepressants may relieve some symptoms. However, both antispasmodics and antidepressants can worsen constipation, so some doctors will also prescribe medications that relax muscles in the bladder and intestines, such as Donnapine and Librax. These medications contain a mild sedative, which can be habit forming, so they need to be used under the guidance of a physician, hope this helps