A master's level project will definitely take more than three months from start to finish. Coming up with a topic is the hardest part. If you could tell us more of your interests then it will help. I usually recommend people find something interesting to them that is related to their job, a problem they have encountered that needs to be addressed. Also, if your project has to have IRB approval then it will take much longer than three months to finish, even if it qualifies for expidited processing.
Look at what has been by other students in your area, oftentimes you can identify a topic in the discussion area of their paper (the recomended future study areas).
Usually a student thinks about a topic during the first half of the program, and actually completes it during the last half. If you were doing a program full time you should expect to spend 6 to 8 months on the project minimum, longer is possible if you are in school part time. Three months for a project is too short for it to be start to finish, unless you already had a topic and a solid basis to start with. If you are implementing some type of intervention, then you will need to leave it in place for quite a bit before measuring results. Additionally, it will take time to determine your methodology for gathering and analyzing data.