OK, so in the last 2 weeks, I've replaced the thermostat and the head gaskets in my 2003 Honda Civic. And with less than 100 miles since repairs, it's still overheating and blowing cold air out intermittently when heater is on. When I got it towed, there was a puddle of liquid on ground by driver's side, back by front wheel level. Any ideas ? This car has 120,000 miles on it and it's been a great car since I got it new. Thanks in advance.

The problem may be corrosion and/or phosphate scale blocking the passages in the radiator and heater core. I would definitely replace the radiator and, at least, reverse flush the heater core. You may even want to replace the heater core. Afterwards, refill with a 50/50 mixture of Dex-Cool and distilled water. These links should help:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-3.html#post235973

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-7.html#post1365453