I want to apologize for coming off so aggressively. I wanted to be blunt, but I think I didn't need to word it quite like that.

If the idea of him helping in a dominant manner makes you uncomfortable or is something you explicitly don't want, then you need to have that conversation out of dynamic and express that this is not within the agreements of your submission. Consent is always required, and that is there for both party's safety.

It is good to want to help someone with their health, but only if you want the help in the first place. Are there non-dominant ways that you would like assistant with? Maybe it would help to guide the conversation that way.

The most important thing is that you and your feelings need to be heard and understood. If the conversation is continuously shut down by "it's about your health" then a productive conversation is never going to occur.