Need help Breathing when swimming

[renu1]

I started swimming about 2 years ago and I would say I have correct techniques. One big problem I have is breathing. It just started to happen recently. When I swim freestyle and turn my head to take a breath, it feels like I can't or am not getting enough air inside my lungs. After swimming, my chest feels like it's been compressed or something. It doesn't feel good. I do blow all my air out before I take a breath so I don't know how to improve on this. I can't swim long distances really well because of this. I'm not sure if it's because I'm not relaxed enough or what but it is really bothering me. Anyone have any advice?