How can you determine where your dex cool is leaking from Leaking very bad not a hose or radiator Possibly water pump but how can i be sure?

Well you can wither do this or have a mechanic do it, you add a florescent dye added to the coolant, then you need a black light to find the leak which will glow under the light. Sometimes these leaks are at the back of the intake manifold which is hard to find. Try using a mirror and looking at the rear of the engine against the firewall and see if it looks wet, feels wet. I had to replace an intake manifold gasket for a coolant leak and that is where it was and very hard to find.