The problem I'm having is to regulate the current down to 1-2 amps.
OK, I assume you're not particularly experienced.
You're building a voltage regulator, so you don't regulate the current (although you might limit it).
What's your experience with electronics?
What is this going to power (alternatively specify the required output in terms of min/max voltage, ripple, transient response, etc)?
You do realise that this power supply could be very dangerous, yeah?
edit: *why* must it be linear?