1990 Other Dodge Models oil pressure dropping out

Dodge RamCharger. When we first got this truck about 6 months ago the oil pressure was sprodaic and would drop down to nothing. Upon checking and changing the oil we found that it had almost 10 qts in it. Changing the oil fixed the problem of the pressure. Recently the oil pressure started dropping out to nothing again. We have not needed to add any oil so we know there is not too much of it again, however when oil was checked it smells like there is fuel in it. Any idea what could cause this? Also it stalls every once in awhile, and has done this since we got it. We were told that the fuel pump was changed about 4-6 months before we bought it.