Are you absolutely sure you followed the correct procedure for bleeding the brakes for your particular model equipped with an ABS system ?
...sure sounds like you have air in the system or possibly its time to replace your rubber flex hoses. ( they are expanding and taking your fluid when pedal is pressed instead of sending it to calipers untill they finally reach a point where they hold the pressure and finally pass it along to the calipers resulting in a weak pedal that gets solid when pumped or at the bottom of travel )

First I would verify you have followed the correct procedure for ABS bleeding your particular model...