2005 Cadillac Escalade esv hvac problem

Hey guys, I'm driving a 2005 Cadillac Escalade esv,
I actually just bought it. But the HVAC system has
been giving me problems. So here is an
explanation of what I have experienced. So I can
turn a/c on for the front and air will come out
sometimes and sometimes it won't, but most of
the time it won't, but when it comes off it turns off
shortly after. Not only that it is not very cold, I'm
assuming the compressor needs a recharge
because I can hear it kicking on and off. I can turn
the back fans on and they will go high or low
according to what I set it too, so that's good. But it
will only blow cold air well cooler ai because I
believe it needs a recharge, but I can not get hot air
to come out which is important as cold weather is
coming and need to be able to defrost my
windows. I've only had the rear vents to blow hot
air one time and that was it.