Well Carol, you could do a couple of things. If you want to try to get some info that will help prevent you from getting a big repair bill, I would suggest that you find out what the code is that is stored in your car's computer memory. You can go to many of the larger retail auto stores like autozone and they will plug in a device called a code reader and read the code for you. You could buy this device for your own use for about $60 at these same places and eliminate the need to run to them everytime you want to read a new code. (I recc. this) Find out the code and then repost to my attention Kevin / HouseCall and I'll continue to help you. You have your homework to do - talk soon.
PS You could also complain the the car lot where you bought it and get them to fix it if you feel they are liable for this problem.