Sniffling, blood in stool & scabs on back

We adopted our 6 year old female kitty Boo-Boo in August. She has had bright red blood mixed with stool here and there, along with regular sniffling and scabs that pop up on her back (near her tail) and ears. The past two times we’ve taken her to the vet they’ve diagnosed her with parasites; first time generalized, second time with hookworms in specific. Her symptoms are still occurring after medication and she’s now throwing up in this second round, likely as a rejection of the medication. We’re about to take her in to a third visit and I’m guessing we will have to run through a lot of testing. Just curious- any experience/advice for similar symptoms in your own kitties?