It is important that you understand that the condition of hypothyroidism
is a chronic condition and you have to take the replacement therapy in the from of drug for life. Once the dose of the drug is adjusted according to the requirement of yours, your TSH level
will come within normal level and this problem of hypothyroidism can be controlled.
The recent problem of stomach pain and headache and irregularity in stools may be related to this condition itself or it can be just some other problem. It is difficult to tell any thing for sure from the information provided.
I would suggest you to consult your doctor who is prescribing you there medicine for hypothyroidism and try to get the level of TSH stabilized by taking the appropriate dose titration.
Thanks and take care.