That's super unfortunate that you called and talked to them. Most states have statutes of limitation set for debt. Depending upon what state you are in, it may have already lapsed. By calling them and talking to them as if you owe it, you've likely just reaffirmed the debt, which means the time period starts over.
The problem is that doctors aren't required to bill insurance companies, and you're legally liable even if they don't. Honestly, the best thing you can do right now is talk to a licensed attorney and not talk to anybody else about it until you do.
If you decide to go without an attorney, your options are, assuming you really did reaffirm the debt, decide to pay the debt or refuse to pay the debt.
If you decide to pay the debt, you can call and talk to the insurance company about what they can do to help you, but you need to be prepared in case they say no.
If you decide not to pay the debt, you essentially ignore it and hope it goes away (not a good idea). The doctor (or likely the debt collector the doctor has probably sold the debt to by now) can decide to sue you to recover the money if they want. If that happens, you'll be back in the needing an attorney spot.
If you decide not to pay, you can try to dispute the credit report entry, although it will likely be unsuccessful. To do that, type a letter to the credit bureau identifying yourself and that you are disputing the information on your credit report. Send it to each credit bureau that has the account on record. You should always use certified mail with return receipt when writing to the credit bureaus. Never use their websites to dispute anything as you have to agree to their arbitration agreement in the process which limits your legal rights.
Again, this is one situation where you really should talk to an attorney. Medical bills can be particularly high, and everything you do, acting and not acting, can affect your legal rights down the road.
I'm not an attorney. This is not legal advice. You should consult an attorney who is licensed to practice law in your particular jurisdiction.