My heater is driving me nuts !

I just got a 1999 323is BMW about 2 months
ago, and the heater is driving me crazy. It
turns on and off by itself. It'll stay really hot
and the AC doesn't work if I were to push
the snowflake button or even put it on the
lowest temp because it's been stuck on the
same temp this whole time even if I change it
and it's probably @ 75-80 degrees. And yes
it does have the anti freeze. When the lights
on the heater control unit come on, I can
decide if I want it on the feet or on the
dashboard. But that's about it. It won't come
out of the front vents. And the temp will flash
constantly and if I change it to my feet, itll
flash for a little, then the lights go off for a
while. Sometimes ikk change it but turn off
and when it turns back on, it resets itself.
But it'll stay on the lowest speed and it'll still
stay on and turn off, then when I accelerate,
the heater turns back on. So I have to open
my windows and that still doesn't help. My
dad disconnected the control unit and it still
stays on. What can I do or what is wrong
with it ? It's going to be summer soon and
having a heater that constantly stays on,
isn't the greatest thing. And I'm on a really
low budget right now. This car has been
costing me a lot lately but I love it.