More info on weird 97

I just took my truck out for lunch and noticed the coolant is low again, this has happened a couple of times now, and I can't see it leaking anywhere, think all the above symptoms point to a blown head gasket ?

Pressure test the cooling system and pay close attention to the intake gaskets..especially in the rear of the engine.

Thanks Merlin I'll do that, I've been watching it really closely yesterday and today to see what the level is and there is about a cupfull a day going out, which is about two hours worth of run time.
And I think it is leaking outside around the back somewhere, but never leaves anything on the ground when its parked, but it may just be blowing away on the highway, think I'll do a compression test as well though just to put my mind to rest.