What you're describing sounds like a textbook case of nipple preference or nipple confusion. Baby has some trouble latching in the early weeks, so mama, not wanting baby to go hungry, introduces bottles too early. Baby learns ineffective latching habits from the bottle, or even comes to prefer the ease of bottlefeeding, because breastfeeding requires a complicated process of movement of mouth and tongue, while a bottle just needs suction.
Baby begins to occasionally reject the breast, and mama relies more and more on bottles.
It's a slippery slope. As you give more bottles, baby gets more and more accustomed to bottles. Your supply starts to slip, because even a good pump can't keep up supply the way baby can.
The ultimate outcome is often that baby rejects the breast completely. This can happen suddenly, or it can be a gradual process that sneaks up on you.
Not all babies are subject to nipple confusion. Some kids go back and forth right from the start with no issues. But other kids are very susceptible, and you don't know who they will be until it happens.
I know this because I dealt with it with two of my kids. With DD1, I lost the battle, and by 2 months old she wasn't nursing at the breast at all. And exclusive pumping is arduous hard work, and not something I'd recommend, and some mamas can't keep up a good supply even with the best pump and pumping regimen.
With DS, we won the battle, and he went on to nurse into toddlerhood (and not incidentally, became an ardent bottle-refuser...

). The difference was that I had the courage, that time around, to throw the bottles in the trash, and go back to exclusive breastfeeding, even though it meant a few really difficult days.
The idea is that you take away any alternate forms of sucking satisfaction-- no bottles, no pacis, no finger-sucking, etc. You nurse as often as possible, in different locations and positions. Do as much skin-to-skin contact as possible. If baby can't latch and gets frustrated, stop trying for ten minutes of so, and then try again.
If baby isn't latching and nursing at least every two hours or so, you also pump, to keep up your supply, and store the milk.
Baby's weight and output are watched carefully. If needed, supplemental feedings of pumped milk are given by alternate methods that offer no sucking-- either with a syringe or dropper, a tiny medicine cup, or a supplemental nursing system that allows supplementing at the breast.
This is best done with the support of a good LC who can evaluate baby's latch and look for problems like poor latch or positioning, tongue tie, disordered sucking, etc.
The idea is that a baby that young has a very very very strong urge to suck, and if only allowed sucking at the breast, baby will return enthusiastically to breastfeeding within only a few days.