Any tips on breathing more easily during freestyle

I am a from Singapore, and happen to come by this useful forum. hope you guys can help solve my problems. Here is my problem: I have been swimming for the past few 3 years now. I would expect my stamina to be getting better, but that dosent seem to be the case. I can swim freestyle continuosly for the first 150m without encountering much of any problems, but at 200m, i find breathing a chore even thou i am already breathin every 2 strokes. I think it may have something to do with my breathing time. Every time i turn to breath, it dosent seem to be long enough as my arms would pull very soon inorder to keep my body balanced, resulting in me having insufficient air. This problems could only be solved when I am using hand paddles which lenghten my gliding time. Is there any way that i can lenghten this gliding time without the use of hand paddles or forcing myself to extend my arms awkwardly for as long as i can? Thanx :confused: