Jeep Repair: 97 XJ with low oil pressure, oil pressure sending unit, low oil pressure

Question
I've found some info elsewhere about this but want more specifics. I have a '97 jeep cherokee, 6cyl 4.0L with 138k mi. i first noticed it's oil pressure would drop intermittently a couple years ago, then i didn't see it for a while. Now, during a recent trip to the snow where i used 4wd a lot as well as went up and down some moderate inclines, the oil pressure has dropped all the way down to below 10 and the check gauges light comes on. it started out kinda intermittently but now it won't rise no matter what.
coincidentally, the last time i changed the oil, i tried putting some oil treatment in it due to a small oil leak near the oil filter. could that have influenced it?
I've already changed the oil pressure sending unit and even spliced in a new plug that it plugs into it thinking that maybe the wires had got messed up somehow. it seems to be running fine and doesn't overheat. i look in the top of the engine where you add oil and i can see actual flow of oil to the rockers (or whatever they are) and when i turn the engine off, i hear all the oil trickle back down. Does this sound like a gauge problem to you or maybe oil pump? I'm broke and definitely try to do everything myself before taking it to a shop to be diagnosed. any help is greatly appreciated.  

Answer
Hey, you really need to actually check your oil pressure with a oil pressure gauge.  I don't know if you can buy one of these cheap or maybe you could rent or borrow one.  You take out your oil sending unit and screw in the gauge and can see what pressure it is actually it is running.  That is the only way to be sure.  And finally the Oil Treatment, what kind was it?, and what did it say it would do? I had a customer that put STP oil treatment in their car and the engine locked up.  When we tore it down the oil pump pick up screen was clogged with sludge from the engine.  They are right when they say it cleans your engine it all goes to the oil pan.  If that is your case, you can pull down the oil pan, change the oil pick up tube and the oil pump at the same time. You will also need an oil pan gasket.  This is not a fun job, it just takes a lot of time and patience, but it can be done.  Hope this helps!