You really need a probate attorney in your state to help you. In Texas, a person in your situation would owe nothing. Generally, there a very specific rules about the priority of debts to be paid by the estate and the expenses of the last illness and funeral expenses are first in line. Unsecured debt such as credit cards are low priority. If the insurance policies were paid directly to you, that money is not part of the estate and does not have to be used to pay his debts.
Was a probate estate opened for your husband?
If an estate was opened for the estate, notice by publication is required. If a creditor does not file a claim within six months the claim is barred. There is also a two year statute of limitations going from the date of death of the decedent.
You should contact a probate attorney in your area and seek legal counsel. You may or may not owe this debt. Certainly a collection company will continue to send you demands for payment if it looks like you will pay. However, you may not be legally obligated to pay anything.
If you do not know of any attorney, the Illinois State Bar Association operates a Lawyer referral service. Simply go to ISBA.org and follow the links.