Thanks for using Healthcaremagic,
You are known case of Hypothyroidism
and detected to have B12 deficiency.
Your loose motions and pain in abdomen suggest possibility of intestinal infection.
It should be investigated with stool routine and microscopic examination and if necessary culture also.
Other differential could be mal absorption syndrome which proper digestion of food is not there.
B 12 deficiency could be easily corrected with oral or inject able form of therapy.
Your thyroid function must be maintained to normal level with supplementation of Thyroxine
Symptomatic relief may be obtained with antispasmodic drugs.
You should certainly visit your physician to take proper treatment.
Hope this helps.
Wish you good health.
Dr. Akhilesh Dubey M.D