Before you do anything, do the cheapest stuff first. Your thermostat might not be working properly.

Get an OEM honda thermostat and get some coolant from any auto store. Total shouldn't be more than ~$20 and it's a super easy fix. Flush the system out, replace the thermostat then refill the system. Make sure ALL hoses are clamped tight and aren't leaking through any small holes/cracks. Since you say your fan is turning on we'll rule out the faulty fan switch for now. Change the coolant and thermostat then report back.