CAUSES? High oil pressure

Well I changed out he oil about a month back
It was registering properly
My car has a oil leak not sure if it's from oil pan or leaking from power steering
So I poured in extra oil I case it was running low
It was marking high before and now it is still marking high
It goes down a tad bit if I'm in the freeway and I step on it.
That's pretty much it but only a tiny bit