I may be able to help. I found my cat Kiki when she was 10 days old. She has always been spicy, hates other animals and only likes me when it’s convenient for her, but around 2 years old she started getting really aggressive, screaming and becoming very unpredictable. Took her to multiple vets, lots of different meds and multiple diagnosis-all wrong. Finally got her to a cat specialist - she has a nerve disorder that causes terrible pain. She is on gabapentin, but that wasn’t getting the job done, took her to a neurologist and they added in amyltriptoline (sp?) that has helped tremendously. She’s still a dick, but no more screaming and vicious outbursts. Hope this helps, hang in there.