2001 mustang gt

Hey all, excuse the name ....it was my first car! Here is the problem: One day while i was driving my oil pressure went from normal to low(0) then back to normal then so on till it just stays low. I did change the oil about 2 weeks earlier and when this occured. I changed the oil pressure sending unit, nothing changed. It still registers as low pressure. I drove it thinking that it was a faulty unit untill the knocking began, so it has been parked ever since(about a month) untill i can get it to a shop and pay for repair. I was told by a friend that the oil pump could have went out...the car has 146k miles on it and I have been keeping up with the oil changes. This car is my baby so if there is any one out there with the same problem the advice will be much appriciated. Thanks again.

Also forgot to mention that after all of this ,that no check oil or check engine light came on.

Buy a manual gage and check the pressure. This is a picture of one.
http://www.autopart.com/tools/toolsmain/tool/T_2001.htm Screw this into the sending unit hole.
If the pressure is good check out the gage. Unplug the sending unit and use a copper wire between it and the gage it should peg. If it don't change the unit in the dash.
If low pressure unbolt the motor mount and pick up the motor and install 4x4's to block up the motor. Be careful and don't break anything. Pull the pan and check for a plugged strainer. I've never heard of a new pump solving the problem without replacing some bearings,but many people try even buy high output pumps. Junkyards always say this but it don't work.

Knocking? That's not good. This sound usually occurs when the clearances within your engine have become so great that metallic parts (best examples are rods and crankshaft) can smack together as the engine rotates. This is a dreaded sound and usually = complete rebuild, especially if it resulted from low/no oil pressure.

Another source of knocking is detonation, which is an extreme form of pre-ignition which I don't believe is the cause of your knocking.