I'm looking for any kind theories on what might be wrong with him.

I have taken him to the vet twice in the last week. The vet says he isn't running a fever, teeth look good, blood tests are normal, and his x-ray looked ok. The vet wasn't sure what one spot on the x-ray might be. She said possibly stools. He is a big cat though and her feeling around with her hands she couldn't feel anything odd.

I have cleaned his food & water bowl and his litter box. He is drinking ok and he seems interested in food but everytime he eats he throws up. He even throws up when he hasn't eaten.

I did catch him eating on my coneflower but he has done that in the past. As far as Google it doesn't seem to be a poisonous plant but now I have it put up.

Next is an ultrasound for him. However i'm really low on money and not sure how much further I can go. I really don't want to put him down because he was fine a couple weeks ago.