Hi,
Can you please post a circuit diagram?
Show power supplies.
You are using microsecond delays, make the pulse bigger, give you stepper a chance to respond to commands.
100us is very very small. = 5Mhz for a 200us period.
Try;
delay(100);
100ms it will let you see if the stepper is being activated or not.
Can you please post a link to stepper data/specs?
Thanks.. Tom.. 
