Sounds almost defo a head gasket or cracked head etc, easiest way to tell is to see if the coolant level has dropped if not chances are it's ok. It's not white smoke your seeing from exhaust rather it's steam where the coolant is getting boiled and then exhausted.

Another way is to check the plugs, if you see one plug is cleaner than the rest that indicates coolant has been in that cylinder which boils, efficiently steam cleaning that cylinder.

Martin