Baby Bottle Trouble

Hey there! So I was just wondering if any of you fellow mommas had a hard time getting your breastfed baby to take a bottle. My baby is 4 months old now and I'm going to have to go back to work when she's 6-7 months old. I've tried to introduce a bottle when she was about 4-5 weeks old and she took pretty okay. It seems something the past months since have stopped me from being able to try and get her to take a bottle but now it's crunch time and I'm not sure where to begin...