I am in almost the same position, 100% league record, still in all competitions, 3 losses all season. Still I have players losing form - usually if they have a bad rating and also if they are left out of games, but not usually if they score goals!

Still, because I'm winning games and watching matches I have enough blue packs to cope and keep morale high. I tend to only use them if morale goes down to poor though, because morale can go up in games as well

If you need more packs, you could try watching videos on FB and iOS app. I tend to go for red and green boosters though, because I use them up faster

Hope that helps :-)