Be upfront and honest. Tell him yes I've been in denial about this diagnosis, but my actions were not making things better for me. I am ready to give meds a chance, but I really need you to listen to me when I say a med is causing issues. I'm willing to try these meds, are you willing to listen?
Also if you have a therapist talk this out with them. They might be able to help you decide what you need to say.
Good luck.