Bad head gasket?

I'm pretty sure its a bad head gasket, but I want to make sure. Been having problems containing coolant for months, just thought I needed to replace the 15 year old clamps but after that it only got worse. I drive my car 14 hours a day doing deliveries, runs fine all day. But once it cools down at night it pees on my laneway. To solve that, I would slowly open the coolant reservoir to let the normal amount of pressure off. Then I don't lose any fluids. I was curious last night and released the pressure last night, then went out 30 mins later and opened the cap again. More pressure! What do ya think?

A heat build up after running is normal,hence pressure. How is your coolant level when the engine is cold ? Maybe you have it over full.. A leak down test will tell if you have a bad head gasket.

thats the thing, its actually reading low. but still manages to leak if not vented. i've thought maybe it had built up excess pressure due to air in the system, but have bled it a few times now to be sure.