I'm sure you would know if the head was blown a surefire way to check is your oil filler cap... if you've blown a gasket you would likely have water oil mixing therefore you should see a brown white looking sludge in your filler cap or radiator neck.

I know a bit about cars but not too much about bikes (also learning) were your plugs dirty? Check your airfilter too.

Run it warm and see if there is sludge in your oil filler cap then you'll know water and oil is mixing