The United States Patent and Trademark Office (USPTO) is an essential resource. The best way to determine if your idea is patented or is in the process of obtaining a patent is to search their website. This can be a daunting task. It will require ingenuity and patience on your part.
A patent cannot be obtained upon a mere idea or suggestion; the patent is granted upon a new actual device. A complete description of the actual device or other subject matter for which a patent is sought is required. When the patent application is filed it is given a patent application number. During the review (which can take years), changes are made to the text of the patent, especially in the claims made for the device and the methods for using or implanting it.
The reviewer also checks to see if other similar devices have been patented and how their claims differ from yours. All this information is available in the public section of the online patent office files. There are other files and sections of the application that are private and may not be viewed by the general public. You can search the patent database here.