1993 Honda Accord coolant leak/heat gauge flucuating

Back in October 09 water pump went out and engine overheated. Got water pump fixed, but when first start up afterwards seems to be a slight miss in engine. Other day noticed no coolant in radiator. Mechanic put about 1 gal of coolant in and did pressure test, but said no loss of pressure but did not know where fluid went. I saw no leakage puddles or such either beforehand. No white smoke in exhaust, oil looks fine. Few days later noticed coolant on top of radiator by cap. Next day top radiator hose blew out. Replaced it and cap. Now heat gage flucuates up high and back down again over and over, but not in red zone and again notice coolant puddle on top of radiator by cap. Seems like a lot of pressure in radiator. Also, top hose is hot after driving so seems thermostat is opening ok? Any suggestions on what to do next?