I would find a new doctor. There’s a reason there are many different methylphenidates on the market — because they all are different in some way, even if it’s just the added ingredients or the delivery mechanism (time-release). Do not accept perpetual queasiness and a side effect — that has to be so miserable for him.
I would find a doctor who will listen to you and your child and try a different medication.
ADDitude Community Moderator, Parenting ADHD Trainer & Author, Mom to teen w/ ADHD, LDs, and autism