You poor thing. My heart goes out to you. This is such a hard thing to have to experience. One thought might be to try feeding her in a sling, because it will hold her so close, you could walk around while feeding her, and the motion may so soothing that it will be enough to mimic the closeness of breastfeeding.
And, if you end up deciding not to wean just yet (do you have some compelling reason why you have to right now? four months seems very young for weaning unless there's some strong reason), using the sling will help you to cope with the frequent feedings, because you can feed her in a sling while doing other things--it can really restore sanity to your life. Don't worry about feeding every three hours--that is not actually that frequent for this young a child.
I also struggled through low milk production issues, and also had a baby who refused a bottle. Actually, we wound up introducing solids at around four months (which is early for some babies, right on time for others -- it just depends), and her weight improved right away with the solids.
It does feel like you are a prisoner to the baby when they are this age. The sling can really help, though. Using a sling, you can go out (especially at this time of year) for walks or wherever, and if the baby needs to nurse, she can do so without anyone being able to see anything. It's a way to get your life back, at least a bit.
I would also encourage you to try La Leche, if there is a chapter close to you. Even if you are determined to wean, they will have helpful advice--they know a lot about weaning.
Good luck!
B.
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