Need brake help! 99 suburban k2500
 

So After searching every article I can read about these brake systems, I have to ask about my specific issue. I have a 99 burb, 2500 454. I did the front pads and rotors myself ( I didn't even open any bleeder screw) just pressed the pistons back In to the caliper to allow the bigger brake pads and now my brake pedal feels spongy and it takes me forever to stop.

It also seems like the rear brakes do little to nothing to help slow the burb down either.

I guess my question is does a spongy pedal mean air is in the lines and how would it get there if I never cracked a bleeder? How do I bleed the abs system without a scanner?