2002 Chevy Silverado low oil pressure

Hello so recently last week I noticed my truck
had dropped oil pressure a bit from 40 to
about 35. I did some research and figured I
should check the pick up o ring. So I dropped
the pan and found a decent amount of sludge
from lack of maintenance from previous
owner. So I went ahead and changed out the
entire pick up tube and cleaned the oil paint
spotless, new gasket sealed up good to go.
Started it and my pressure was back and
raising as I drove it, problem solved!! Next day
I drive it and notice pressure is bouncing a
tiny bit nothing below 35 so I head home to a
oil leak on my driveway automatically
assuming gasket I look under and find that the
under side of the truck was covered in oil. Not
from the gasket as it was dry all around.
Between work and home didn’t have the time
to diagnose it I took it to my well trusted shop
with amazing reviews for years. They came to
the conclusion that it was the oil pressure
switch was leaking so I went ahead and had
them replace it (was not leaking before
changing pick up tube) so today rolls around I
pick it up after they had closed due to getting
off work early start it and find that my truck
now has oil pressure below 20 and doesn’t go
above 25 when I’m driving . Would this be a
faulty pressure switch? Maybe another issue?
Any insight is helpful as I called the owner
personally and he says it’s probably fine and
that those guages can be off sometimes. I
don’t think so as it has always idled at 40.
Don’t notice any drops since I’ve been home.