So frustrating

I was playing in a $30.00/9 person sit-n-go. Down to 6 players. I am one before the button, I have A/K unsuited. The blinds are 25 and 50. I raise to 300, I get 4 callers (WTF??????)......the flop is 3,3,7. Here is where I do something really stupid. I go all in, I figure these other people are holding big cards....the flop did not hit them, so I go all in......the first 3 fold (as expected) and the forth calls, with a SOOTED J7. That's right, he called a 300.00 bet with a flippin J7. I deserved to lose.