Overheating Subaru Legacy Outback 1995

I have an Subaru Legacy outback, it has about 194,000 miles on it and it started overheating when it was at about 190,000 miles on it. I changed the radiator and it was okay for a while but began to over heat again. I changed the hoses on it to see if that helped but nothing. When I looked at the coolant it had some kind of grayish texture to it and there was sometimes little chunks of it in it. I flushed out the radiator and hoses and it did nothing but get the greyish texture out of it. I changed the head gasket already and the thermostat 3 times but still it like to suddenly overheat. I recently took out the thermostat and now it doesn't over heat but now I have no heat and that no fun in the winter. Is there anything I can do to help fix this problem with the overheating?