Am i supposed to tell my doctor that i've tried ritalin (methylphenidate)?

YES..tell everything: If you want to get help with regards to your health, well being, treatment .... You have to give a detailed history including most confidential ones, e.g. Alcohol, drugs, smoking, habits, etc.

Yes: You should never take a medication, especially one as potentially dangerous as ritalin (methylphenidate) for people with some medical conditions., without speaking to your doctor first.