Is this a new problem? is your pressure sensor good? Do a mechanical gauge test to be sure. If it is reading correctly, you could have a worn oil pump or the lower bearing could be leaking pressure. Most people will advise against "snake oil" but you could try some lucas oil treatment. It actually works.
This article recommends sea foam to remove sludge, http://www.topix.com/forum/autos/jeep/T34SK6I5JMU8792QI
I never used it so IDK if it works or not.