Hey Rebecca!! I suddenly couldn't get much from the pump either... and they say that babies are much more efficient, but I'm not so sure I really believe they are really all that much more. BW says baby can get about 1 ounce more than you can pump - and I don't think when my supply was dwindling that she really could get that much more, simply b/c of the ratio: if she could normally get one ounce more when I can pump 5oz, then she logically would only be able to get 1/5 oz more if I could only pump 1oz, kwim? Cuz if you used to be able to pump 8oz and now you can only pump 4, there's no way it's just b/c he's more efficient than the pump and he's still getting 8oz, IMO.
If you want to feed him from a bottle for a day, first count everything he eats for 2-3 days b/c just b/c you give him a 6oz bottle and he drinks it all doesn't mean that's what he's getting from you... you'd have to see if his solids decrease too. And you'd probably do better to do the experiment over at least 2 days, not just one, IMO. And even then, I'd probably combine that info with a yield to get a better educated guess.
As far as whether to feed him 100% bm as long as possible or to combine, that's completely up to you. I think there are probably benefits both ways, but one thing I'd definitely say is that even if you decide to do BM ALAP you might still save some for the transition and start introducing formula before you run out. They're not lying when they say poop changes (although Charlie's probably already has since he's on so much solids) but I did notice that any time she was constipated if I gave her BM for a few bottles, it would help things pass through.
Argh!! SO hard!! Maybe I'm being paranoid and over thinking things, but i just don't know.
I don't think so, IMHO. You are almost 4 months pregnant and your body is trying to get ready for Baby#2. It's normal and natural for your milk production to slow/stop and ultimately change to colostrum. I know it's hard to accept, believe me I *know*. And it's SOOOO hard to give them that first bottle of formula. Well, it's hard to give them any formula, but especially at first. But you have done an AMAZING job of doing everything you can to keep up your supply and do what's best for C. And you had great foresight to store up as much BM as possible - you did great and it's not over yet, it just might be time to start supplementing, either with FF or your EBM b/c you do want to do what's best for Charlie and if you think he might not be getting enough BM that's not good for him.
I'm definitely not trying to be negative here, so please don't think that. I'm just trying to be honest and from what you have said it definitely sounds like there is cause to be concerned about the amount of BM he might or might not be getting. Especially since you are nearing your 4th month already, kwim?
Posting at the same time as CM -
And I've heard too that milk increases in the 3rd trimester, BUT it's still colostrum until after the newbie comes...