Your stepping is not correct. coilA and coilB should be driven like this:
00 -> stepdelay -> 01 -> stepdelay -> 11 -> stepdelay -> 10 -> stepdelay -> 00 ...
To change the direction of rotation, the coils must be driven in reverse order.
Which voltage do you apply to the coils? With the ULN driver this must not be more than 5..6 Volt.