Current mode buck regulator design
Your current sense will be an RL charge/discharge waveform, and the fastest loop frequency for your regulation is going to be limited by the fastest rate of A/D conversions for your MCU. 
Since you have no output capacitance, your current detector is measuring the peak current (and only then after an ADC delay). The rate of current rise through your inductor you should be well equipped to calculate (hint, the inductor is too low a value for what can be achieved inside a MCU loop)

I'd suggest that you also need a capacitor from Pin 1 of your connector to ground which will reduce the peaky waveform you currently have and help you more reasonably control the current.