Legal Help! Do you think I have a case?

Your insurance company is talking rot...it may have been a pre existing condition but it hadn't been diagnosed so you were unaware of it when you took out the policy Tell them you are going to sue them on that basis (they are in breach of contract) you could also think about suing the doctor for failing to diagnose your condition within a reasonable time, although I don't know whether you'd have any success there...you should see a lawyer.