When do I pump while still bf'ing.

RachelEric

I just purchased a manual Ameda breastpump.  I want to start pumping for the occasional bottle so DH can feed him a bottle once in a while, plus, I want to start a stash for when I go back to work in a few months.  My question is, when do I pump?  I feel like if I pump before I feed him, then he won't get anything.  If I pump after I feed him, then I won't pump anything.  I don't know how much to pump, and I never know how much LO is getting (i've been exclusively bfing), so how do I know how much he needs?