oil pressure

I need some input. My truck has a slow constant oil leak. This, however, is not the problem. I continue to add oil as needed. The thing is that when the oil gets low my pressure gage goes up. Sometimes it drops below normal and other times it jumps all over the place, but mostly it is always above normal. What does this mean?

If its always somewhere between 20 and 60 dont worry about it.

i'd say air is going through the oil pump and getting compressed& expanding