This exact thing happened with my daughter, and I also provide childcare for an infant who is breastfed and had never taken a bottle prior to coming to my home, so I have some experience with this. My dd was about 3 months old too, and out of nowhere she stopped taking a bottle at all. When we would try she would cry/choke/turn her head and it was a very dramatic scene. We fought it and fought it, but what finally worked for her was taking a month off totally from trying the bottle (I'm a SAHM). She had developed such an aversion to it that it just wasn't going anywhere, and I was getting worried that we were creating issues around eating. After taking a month off, and then trying again, she now will take a bottle (a little bit-when she feels like it lol :)). On the other hand, with the baby I take care of in my home, we didn't have the luxury of time, because she is here for 10+ hour days. We tried about a million different nipples and finally found one that worked-it's actually a cheap, disposible nipple (Enfamil) like they give out in the hospital. For whatever reason, it's the only one that she will take. I also, in the beginning, had to hold her in a different position than her nursing position, because when I would hold her in the traditional "baby hold" she wanted to nurse. Sometimes I will still actually have to feed her in a bouncy seat, or facing me in a boppy, to get her to take the bottle. One final tip-heat the bottle up very warm, much warmer than room temperature. Both my dd and the baby I care for will only drink it very warm. Good luck!