How can I overcome the breathing trouble while meditating and increase concentration?

At certain point of meditation,I feel like I can't breathe properly as in the beginning of meditation(lose of oxygen) and thus I stop meditating and try to get oxygen into my brain. I do no know why this is happening or how to overcome this condition. Is that not a correct way of meditating? Or what am I doing is wrong ?Or do I have to push through?