Cooling system

I have a 2005 Ford Explorer I know I have a leak but
I'm not sure from where though. When I drive long
distances my car overheats badly and when it
begins to do that I turn on the heat because that
draws heat from the engine it helps sometimes but
the next problem is no hear ever comes out it blows
cold air also my overflow tank ( box where cooling
goes) drains very fast when I put cooling in it leaks
out immediately so I bought bar's leaks liquid
aluminum stop leak