Wa'alaikumassalam sis, I understand how stressful this must be for you especially when you're working and trying to maintain breastfeeding. At 3-4 months, babies sometimes go through a phase where they reject the bottle, it's quite common and usually passes, so please don't worry too much. Have you tried switching to a slower-flow teat or a bottle with a softer, more breast-like nipple shape, as sometimes babies prefer bottles that feel closer to nursing? You could also try expressing a bit of milk onto the teat first so he smells and tastes it immediately, or ask your caregiver to try feeding him when he's calm and not too hungry, sometimes a very fussy baby refuses the bottle simply because he wants you. Hang in there, mama; many of us have been through this phase and it does get better.