1997 Jeep Wrangler Low Oil Pressure

1997 Jeep Wrangler 4 cyl Manual

I'm no car pro, but I love my Jeep, so I would love help trying to figure out my problem. Normally when in neutral the oil pressure gauge sits at 20, when I shift in gear and accelerate it goes up to 40, and when I switch between gears it pulses from 40 > 20 > 40. Recently it's been sitting at 20 when in gear and just below 20 when in neutral. I got my oil changed about 2 months ago after my brothers let the oil turn to sludge for a year, and when I checked the dipstick to see if it needed oil, there was actually too much oil. The car runs fine, but I do sometimes smell burning oil, however no smoke from under the hood. I don't know if I should stop driving it until I figure out the problem. Please help!