unfortunately no company covers pre-existing conditions.... that way they would be out of business i think, lol.
I am sorry your doggie is sick.. I don't have any advice im sorry..but im sending positive vibes your way!
In regards to pet insurance...I think it's extremely beneficial to have. I've been able to save money on all the vet bills we've had for the past year with it. I have Trupanion pet insurance and they've been great, affordable, and cover 90% of our vet bills, meds, and sugeries.
Worth checking them out at least. ww.trupanionpetinsurnace.com