Was it negligent for my doctor to give a pre-diagnosis of cancer before eliminating other possible causes of my illness first?

It *may* have been negligent--the issue is what would a "reasonable doctor" do in that situation? If the average well-trained reasonable doctor might have referred you directly to a specialist, then it's not negligent or malpractice. There are valid reasons, by the way, for doing so, so it is unlikely that this was malpractice: for example, with cancer, time is often of the essence; a delay in treatment can be a death sentence. It is often the better practice, if cancer is suspected, to immediately send someone for further evaluation, screening, or treatment, on the grounds that the "damage" done by unnecessary follow-up is much less than the damage done if cancer is ignored and takes further hold. Also, even if it was negligent, the most you could recover in a lawsuit, if you were not actually injured or sickened by being sent to the specialist, would be whatever out-of-pocket medical costs you incurred from the unnecessary treatment.