Coolant Leaks
 

This is a 2006 H2 with about 170k mileage.
First had a leak at one of the heater hose connections (the 3-way connector). Replaced it
Right after that, the radiator started leaking. Replaced it along with the thermostat and reservoir cap (thinking of high water pressure)
Now the water pump is leaking
Not sure what's going on. Any idea?

170k miles is what is going on. Those are typical issues for the mileage, you should replace all your radiator/heater hoses at the same time.

Could be as phil mentioned. All of that stuff is 15+ years old. After that much time rubber seals, hoses, plastics, etc all start to degrade and go bad.

Pressure is also a possibility though and is a common symptom of a head gasket leak. That can cause high pressure combustion gasses to be forced into the cooling system. Hopefully that is not the issue but you can get a test kit to verify that pretty cheap.
Another spot to be very aware of is where the heater hoses attach to the bulkhead fittings at the firewall. The plastic on those are very prone to dry rotting and breaking off (the plastic connector part on the ends of the hoses there). One slight tug on those heater hoses can break them easily but they are cheap from the part stores to get replacements.

Thanks Mixman..will check out the pressure before anything else. Hopefully, its as easy as u implied and the kit comes with an instruction

The old method to check is to just remove the radiator cap and run the engine while watching for a near continual stream of bubbles coming up. But that method probably will not work as well on the H2 since the cap is one the overflow tank. The type of test I lined does work great too - that one detects actual combustion gasses in the coolant.

Is that the test using the combustion leak detector sold on Amazon?

Yes the one I linked on Amazon will be the best option.