When replacing brake pads, brake loses its grip
This may not be an answer but it was too long to comment.

When you compressed the pads did you open the system? Meaning uncapping the reservoir, or did you simply push them back without doing anything else? Sounds like air has gotten in the system and it will need to be bled. 

One of the steps of bleeding is creating a vacuum to pull air out of the fluid that isn't normally visible in bubble form. If the caliper pistons are pushed back without opening the system you may have done the opposite in a way and pressurized the system, then upon pulling the brake level you may have recreated a vacuum that pulled air from the fluid and caused an air bubble internally. That's the best way i can think to explain it anyway.

'Tis but a guess on my part but it sounds like a bleed is needed either way.

Pulling the brake while there is no pad or bleed block in there is also a no no and will lead to having to bleed the system.

Bottom line, bleed it or pay to have it properly done and i bet you're back in action. Also don't get fluid on the rotors or your new pads. and follow a proper bed in/burn in process.