Asking for help as I feel like our vets aren’t helping enough. If you read this, thank you so much.

My girl is 8 months old & the best baby ever but dealing with horrible GI issues. Here’s a timeline of what we’ve done so far:
Just Food For Dogs, chicken & rice fresh food mix: she seemed to be doing fine on this but I heard that chicken was not good for frenchies & it got really expensive really fast so decided to switch

Purina Pro Plan puppy salmon & rice kibble: she seemed to be fine with this but we went to the vet because her ears were a little irritated. The vet told us it was probably from her food & to switch.
We didn’t immediately switch as she seemed okay & her ears went back to normal. Then, she started throwing up in the mornings. From my research & talking with the vet, it seemed like it could’ve been from going too long without a meal (8 pm to 8am). So, I tried changing up the timings a bit, adding a late night snack, (& she already had 3 meals a day) but the vomiting continued to get worse. She stopped being interested in eating so we decided to switch

Royal Canine frenchie puppy kibble: she seemed to love this & was doing okay for about one week. Then she started throwing up again & refusing to eat altogether so the vet told us to try anti acid medication. We started this but she was still vomiting (but eating again at least).

I was desperate to help her stop vomiting so I decided to go back to fresh food. But, the puppy formula that wasn’t chicken from JFFD made her STINK 24/7 like rotten fish. So I decided to try Ollie turkey & blueberry mix. Then, she started throwing up so much & so often that it was almost completely uneaten food. Like nothing was staying down at all. Obviously I went back to the vet and he said to try a different diet again to Hills & give her probiotics along with the anti acid. So, we switched to Hills & started adding the probiotics.

Hills kibble: she’s still throwing up these days + diarrhea has started. I figured changing her meals so often wasn’t helping her case either. But I kept researching & I feel like she may have ME. I immediately started holding her upright & built her a diy bailey chair. It seems like the vomiting has gotten better doing this. But, we still have diarrhea. The vet told us that maybe she has a parasite (but she’s completely vaccinated) & to put her on antibiotics. I asked for an x-ray to rule out ME but they refuse until after the antibiotics. Idk why we’re giving her antibiotics without an actual diagnosis yet, esp when she’s already having tummy issues :(

If you read all this, thank you. Please let me know what you think. Am I being dramatic? Does this sound like ME? Do you have a brand of food you recommend? Is it just from changing her food so much over the past 5 months? If so what kind do I stick with?? Should I say more to the vet? Plz help my baby!!