Truck is leaking oil bad

What is your question?

My 1993 1500 Silverado was running great. it was due for an oil changed so I pulled it in the garage drained out old oil and put 5qt of 5w-30 in and a new oil filter.(while I was under there I also greased the front end) when I pulled the truck out of the garage the oil pressure was reading off the gauge. I though I had gotten a bad oil filter so I replaced it and when I started it up again it was pouring oil out of somewhere (only when running) I have not had a chance to investigate further but it appears to be leaking from above the oil pan. any suggestions?? thanks