My iphone 4 turned off and wont turn back on. I HAVE TRIED DFU MODE.

I was using my iphone 4 today when it just shutoff, I tried turning it back on by using the power button. I tried turning it back on by holding down the sleep button and the main button at the same time for over 30 sec.I had it fully charged but it still wont turn on. I put it on the charger for about an hour and it still wont turn on. I havent had any problems liek this on my iphone before. I havent dropped it, I havent jailbroken it. I have tried DFU. any other suggestions?