1998 Nissan Maxima brakes

1998 Nissan Maxima 6 cyl Front Wheel Drive Automatic

I just changed my brake pads on my front and back. I had no problem with the fronts but the back ones gave me trouble. I couldn't get the pistons to go in even after renting the right tool. I bought two new calipers to replace the old ones that weren't cooperating. I put them on and bled the breaks. I've only gone up and down my drive way and the pedal still goes down further than it should and the breaks are working on and off, the e brake is working right though. Do I just need to keep bleeding the breaks?