Check your oil and see if it has coolant in it. My car did the same thing you are describing and eventually a piston disintegrated from the increased pressure the coolant was creating from foaming my oil.

I would not drive your car unless you absolutely have to.

 

The car is parked for now. Need to order up a waterpump and headgasket. As for the o-ringed head, where can I find replacement o-rings? Is there a standard size or am I best off measuring them when I take the head off?

 

Your O-rings in the head are metal and should stay in the head. They aren't much more than a thin wire but they do make different ones. You probably need to take it to a machine shop.