If you are seeing a physician what diagnostic imaging studies have been conducted, what is your diagnosis and prognosis, and what is your physician's assessment for why you are not recovering from your injury? A soft tissue injury should resolve much more quickly than you describe.
Is your chiropractor merely doing chiropractic adjustments, or are you also receiving physical therapy? Are you on a home exercise program? Are you compliant?
On the positive side, if you go to a chiropractor once or twice a week, odds are the chiropractor has documented your condition and complaints at each visit such that you can show a continuation of symptoms from the time of the accident. On the negative side, chiropractic care is viewed skeptically by insurance companies.