In response to the headache issues, the only time in my life that I was on Ritalin was in elementary school. The medication made me so sick with massive headaches that I was in the nurse’s office begging to go home every day. I have been off medication for the last 20+ years since and managing my special brain via behavior only.
Definitely discuss the headaches with your doctor. The fact that you’ve found water helps might be enough of a strategy to manage them if you find the Ritalin helpful, but a good doctor should be able to discuss that with you to make sure it isn’t something more serious and help you tweak treatment as needed.