general problems of the 2002 Mercury Cougar

I have firestone fire hawk tires on my 2002 Mercury couger xr. The tire model number is 215-50-17. My car has 44,000 miles on it. I bought it new and I have had 5 flat tires on the front two tires of my car. The rear tires have 44,000 miles on them. Each time I get a flat tire, the tire is shredded in the inside and I have been lucky that I was driving in the city not going very fast. I have been told every time that my tire pressure must be low and therefore caused a flat. I got my 5th flat tire in 4 yrs on 11/22/07 (thanksgiving). My tires had just been check when I got my oil change two weeks before, but I still got a flat tire. I had just been driving on a hwy going 65mph and I am thankful it didn't happen then, I am disabled and the road I had been driving on was in the middle of no where. Soon after I return to town I got a flat tire. My husband was then in the car with me. I took the tire in to pomps tires the same place I have always taken them, and the tire was again shredded. I am not sure if anyone else has had this problem but I truly think these tires are defective and dangerous.