Always read your contract but they can probably repossess your vehicle after one day of a missed payment. Look for technicalities such as how many days after the payment is due do you incur a late fee, and look to see if the contract has any language in it about repossession and when. You can hire an attorney to interpret the contract for you if you would like. You can contact an attorney to file for bankruptcy. In all likelihood you are only paying interest and you would be better off in a chapter 13 because a 13 reduces the interest rate.
There are many factors that can affect how best to handle this matter and the best advise is to hire an attorney immediately. Unfortunately the advice above is a guess that is based on very scanty facts. Circumstances of all sorts can change the ultimate answer you need. If you want to know how best to handle the situation, make an appointment with an attorney and get good solid advise based on more exact facts. The money spent might give you the peace of mind you need.