Struggling to be heard by doctors

You honestly have to seize power as weird as that sounds and how hard it actually is. You gotta remember, they work for you not other way around. They can be fired if they aren't giving you what you need from them. If they are refusing testing, tell you that it's all because your plus sized, or just gaslighting you here's what you do. You say to them "I want you to document in my medical chart you are refusing to provide services/tests that I am requesting" if they try to argue repeat it, making it clear you want their refusal documented in your chart. Even if its they trying to tell you that if you lose weight it'll fix everything. They are your employees, they either do their job or you have them document they are refusing services because of their fat phobia. This can also make them change their tune quick as they can get in huge trouble through the hospitals and board.