Omega B – Y32SE – Coolant loss

Have some time problems with cooling water loss I have to tip back every 10km 0.5 liters nowhere where it drips even if the car is warm, has gas plant of BRC inside 335tkm on the hump, if gas give excessive white exhaust gases it may be that the head seals are flat (despite that really bad) or have her tips for me thank you in advance