If you really want to protect your right to use your business name and associated intellectual property or goodwill, it is absolutely critical that you register your marks with the United States Patent and Trademark Office.
There are lots of things that you can do with your shiny, new, registered mark.
First, you get exclusive, nationwide ownership & right to expand using your mark. Second, the USPTO will, henceforth, kick out future applications that infringe on your mark, meaning that no new similar or confusing marks will be granted. Third, if someone does infringe on your mark, you can bring a lawsuit in big bad Federal court to enforce it. Fourth, while in Federal court, you can recover profits, statutory damages, attorneys fees, or treble damages based on willful infringement.
Do you HAVE to REGISTER your mark to have these rights? Yes and no. If you’ve been using your mark for 10 years without registering it with the USPTO, you may or may not have some of these rights. But any rights or protections you do have will most certainly be limited, and not nearly what you can get with an actual registration with the USPTO. So, bottom line, register your trademark.