If you have a RED/Green "Tank empty" indicator on the regulator, then turn off everything and open one tank valve, the indicator should go green, close valve and check tomorrow, should still be green
If you have not, then open a tank valve till you hear the hiss of gas flowing, Ok, open all the way then close, come back tomorrow and open slowly, did you hear the hiss of gas flow again? (You should not) note that this is not as good as the first version.
You can get in in-line pressure gauge from most places that sell RV's
Nothing adds excitement like something that is none of your business.
2005 Damon Intruder 377W Radio Active as WA8YXM