There are a couple of things going on for you probably. First off, you are most likely in the honeymoon phase. It's an unpleasant phase where your pancreas still sporadically produces insulin. More some days, less on others. Your residual function will eventually decline, your insulin requirements will go up (don't panic) and things will settle. On the other hand, nothing is ever completely stable. Thanks to all sorts of other factors like weather, mood, hormones, exercise, etc, you may do the exact same thing 2 days in a row and get entirely different results.
The bottom line is that you will do the best you can. Try to keep things stable, bolus when you are high, take some juice when you are low, and basically just be as active and enjoy your life to the max.