Hi Fletch,
Just a word of caution, if you start adding formula, you are telling your body to produce less milk instead of opposite. The best way to increase supply at such an early age is to nurse as often as your baby asks for it, supplementing with formula may cause more problems. This would be only recommended if you wouldn't be able to produce any milk at all but this is rare. At 6 weeks many babies go through a growth spurt and they need to nurse more often to increase supply. If you give some formula at this time, your breast will not be stimulated enough and in the end you will have less milk.