DON'T USE FORMULA TO SUPPLEMENT UNTIL YOUR MILK COMES IN!!!!! Just let your son nurse as needed. Yes, it SUCKS, yes, you get exhausted (I was so tired i hallucinated) but the more he nurses, the more milk you will have. Any supplementation you use (paci, formula, etc) will inhibit your milk production (although my son used a paci and I'm still nursing/pumping successfully).
DON'T GIVE UP!!!!! Unfortunately, you will be doing LOTS and LOTS of stitting around at this point, but it is SOOOOO worth it. At 10 days, he will have a growth spurt, and it will never seem like he's getting enough, but it's NORMAL and worth it in the end.
Please PM me if you have any questions....everything he's doing is normal.