Ok, it's about 0 degrees out and my engine still overheats. What can I do? I keep putting more and more antifreeze in it but it doesn't want to keep it in. Does the overflow and cap need to be above the radiator or can it be even with it? What else would cause it to do this?

97' 2 Door Blazer, 31x10.5 BFG A/T KO's,
2" PA Lift, Air-Aid Intake, Custom 3' muffler.