Wall and ceiling paint that leave white lines.

I bought a 20liter Duram wall and ceiling paint - Summit colour - to paint my lounge and I am on the 3rd coat now and the paint leave white marks. the paint was stirred and new roller and tried everything it keeps on making white lines. This is the worst paint ever and I am not a millionare to just buy new paint. I will feel ashamed to let anyone enter my lounge due to this paint. Nothing help or works. Today i tried a 4th coat paint and it still is the same. I bought the paint at Mica hardware and they cant help me.