I would say that the FF will probably affect your BF. When I started comp feeding at 6 weeks my supply went down even more and I ended up ful time FF at 12 weeks. Also don't believe people when they tell you that a FF baby sleeps better - it's a myth! My DS has only started sleeping through the night in the last 3 months and he's almost 20 months old now!

I'm certainly no BF expert but I think try extra BF and see if this makes any difference.