Dear Welcome to HCM We understand your concerns I went through your details. I suggest you not to worry much. Ritalin (methylphenidate) is a central nervous system stimulant. It affects chemicals in the brain and nerves that contribute to hyperactivity and impulse control. Stomach pain, nausea, vomiting, upset stomach are side effects associated with this drug. please consult your psychiatrist for further advice. Please post a direct question to me in this website. Make sure that you include every minute details possible. I shall prescribe some psychotherapy techniques which should help you cure your condition. Hope this answers your query. Available for further clarifications. Good luck.