Progress is contingent on your fitness level, age, type of equipment you're riding and general ability to adapt to new exercise. It sounds like you're doing some impressive riding for a newbie, however.

It is important to develop good cycling habits in the beginning. Your muscles have memory. If you are serious about becoming a good cyclist, get some clipless pedals or toe cages. Those allow you to pull up on the pedals as well as push down. Keep your cadence high - ~80-100 rpm's. This allows your tendons & ligaments in your knees, hips & ankles to become accustomed to cycling. Your muscles will become stronger before your connective tissues become stronger. You want to avoid any nagging injury from the beginning.

You said you're riding a cyclocross bike? And it sounds like you're riding off road, is that correct? I'm a roadie, but we have some experts on this board who are off road cyclists.