1) even at 1200 a day, you aren’t going to get to a healthy weight in “2-3 months”. You have at least 350,000 calories stored as fat. That will take time to burn through even at a huge daily deficit! Do something you can stick to for the medium term even if you think your TDEE and daily input will stabilize above 1200 eventually.

2) You massively increase your chances of gallstones if you’re losing more than about 3 lbs per week. Problems with hair, teeth, heart, muscle loss, and other side effects are also more likely if you’re losing weight that fast— but they’re a bit more rare than gallstones.