i just want to add that you are headed for a growth spurt soon, they are designed to increase your supply.
I agree with feed, feed, feed as an alternative to pumping (i never really got on with that) and the formula.
I was always told that even if a baby takes a full bottle of formula after a feed, it is not an indication that the baby was not satisfied, it was a natural sucking reflex. Others may suggest pumping an seeing how much you pump - it is not a true indication of your supply, a baby is able to suck so much more that you could pump, they are so efficient. I was never able to pump more that 1oz EVER.
Make sure you are drinking enough, rest when she is resting and eating enough. I know you are worried about the housework / laundry, but you need to put milk first.
Last thing - I was never really aware of my letdown after a while. just because you can't feel it anymore, may be more of an indication that you are adjusting to bf and not a dwindling supply.
I have said much more that I thought I would.
Hope I have made sense.
alex