Truck

someone cant tell you that you have no oil pressure w/o a gauge. and if you had no oil pressure.....you would know real quick. you will know by a few loud sounds that dont sound good and it wont start again. you have an oil psi gauge on your dash....
 
how is it running? is it running hot at all? sounds stupid but check to see if one of the spark plugs have come loose. It sounds like a huge exhaust leak if they are and u would obvioulsy loose power/compression. if it is running ok maybe a really bad exaust leak??? good luck

Nick