fumducker

1 have a 2002 nissan sentra. 150,000 miles. maintained good. replaced plugs about 50,000 mi ago
now service engine lite is on, misses when 1st started or raining,
but the biggest problem and this could be related to missing is about once or twice a month i gotta add water/antifreeze to the radiator and or reservoir
i cannot see any leaks is heater or radiator hoses
would it be head gasket or head crack?
thanks in advance for help