Brake help!!! Danger!!

[ScottyTightdog]

So I rebuilt my drum brakes this weekend. Everything new drums, cylinders, all new small parts/springs/etc. I go out for a test drive and initially they weren’t great but I assumed it would take a couple stops for them to grab. As I thought they started working pretty good after a couple slow stops. Took it on the highway and hit them pretty hard a few times with good stops. So I headed back to the house and as I was coming to a stop sign I hit them and had no stopping power!!!! Just had to roll on through, pedal was pretty firm, tried pumping them but had no stopping power. Went down the road a little and they worked fine again. Worked several more times until I got back to my street and same thing happened had to roll right on by my driveway and fortunately I was going slow enough to make the u turn in my cul de sac. So any ideas on why they would work fine and then not at all?