1987 Chevy Cavalier

I drive a 1987 Cavalier, and just had my head gasket replaced in November. Earlier last week I discovered my coolant was draining from the engine and I am worried as to what this could be. The (Main) leaking seems to be taking place while the car is parked (it drained last night)
The engine is also not preforming well when I first press the accelerator, it will speed up but if I have to let off before it switches gear (I.E. Stop and go downtown traffic) it will stutter and try to stall, it has only stalled four times out of many, but each time my heart stops a little. It also does this whenever I go into reverse and use the accelerator. Also it has had a squeaky belt ever since when idling, if this is relevant or not I am unaware.
I do not know if these are connected, but would like to know what I am looking at before I take her in or not.