It is absolutely possible in 3 months!
I used about 3 months to prepare and i got 5 AT. But that 3 months was a bitch! 2 hours/day during weekdays; 6 hours/day during weekends.
The two books i used are "Rita's" and "All-in-one PMP Exam Prep Kit: PMP Book, 8 pages Quick Reference Guide, and 340 Flashcards Based on Pmbok - 6th Edition by Sohel Akhter". I did use PMBOK but only as a reference.
One good thing about Sohel's set is you can carry the flashcards with you anywhere you go. That really helped me since big part of the test was based on memorization.
Let's say you have 12 weeks; you should use 10 weeks to finish the 2 books. Set your reading schedule weekly and force your self to finish reading and exercises assignment daily. Do not compromise and do not get distracted if your friend called you to hang in a bar tonight. NO! haha
The last 2 weeks you should use the simulator. I finished the 7 mockup exams in 10 days ..... 4 hours a day taking the test + 1 hour to review the wrong answers. Do treat the mockup tests like the REAL PMP test and finish one by one in 4 hours. Most importantly, understand why you got it wrong in the first time. I never took those tests twice.
I only got one 80% in taking mockups; others range from 72% to 78% but did see improvement each time.
I think the key is to set up a realistic studying plan which you can stick to it; and fully and correctly utilize the simulator.
In the end, "where there is a will, there is a way". You can do it!
