RGP lens too small?

Ive been at my optometrist's office every week for the past month and a half trying to find the right fit for my RGP. The first pair I had for less than a minute because my opt said my iris was too small for it. So he orders a new one at a really small size of about 8.2mm. They pop out and roll around my eye for the next wk. I tell my opt and he says that's fairly normal but when we do the exam, my vision is completely askew and he has to change my prescription which was completely perfect with the old lens the week prior. He also admits maybe he sized too small.
Now I have a lens that's 8.5mm, but still rolls around, though it doesn't pop anymore. My opt clearly doesn't believe what I tell him when I report back to him but I'm already on my third trial pair and my vision (which had be stable at -3.25 and -3.75 for the past five years) has suddenly jumped a full point back for both eyes within a week.
I want to ask him to give me the regular size since I didn't even have a chance to feel it's fit for over a minute.
While I don't want to be rude, he's inconvenienced me for over a month, has no experience fitting rgps (I'I his "first," as he loves to remind me), and has caused damage to my vision (my assumption of course of wearing too small lenses and worsening prescription). Is there anyone there who can advise me? Idk if I'm being just frustrated now or if it'd be a good idea to kindly suggest and maybe assert more how I'm feeling to him since he usually disregards my complaints.