It's normal to get burnt out on a job over time. If you haven't changed positions in any way, you're bound to get bored and feel like it's time for a change. That's not necessarily a bad thing, but if you want to stay at your company, an article by the New York Times suggests expanding your job description on your own.
When you get stuck in particular roles in a company it's easy to lose sight of what you actually enjoy doing there. Eventually, you feel like you've reached your limit and it's time to leave. Speaking with the New York Times, psychologist Adam Grant suggests that if you need to stick around you need to hunt down more interesting projects:
I usually judge limits on years of work experience by whether you're continuing to learn and gaining responsibility and impact. When your development stalls, and when your contributions don't expand, I think it's often time for a change. Many people assume that this means finding a new role, overlooking that meaningful change can occur in the context of an existing role. Amy Wrzesniewski, Jane Dutton and Justin Berg have done fascinating research on job crafting, the ways that we take initiative to modify our own tasks and relationships -- adding projects that are interesting or challenging, delegating and swapping tasks with others and choosing to spend more time collaborating with particular people. They've developed an activity, the Job Crafting Exercise, in which you can map the key building blocks of your job, and then formulate a more ideal -- but still realistic -- plan for crafting your job to align more closely with your interests, skills and values. It's also an excellent way to identify new ways of adding value.
Helpful Workplace Hints From the World's Most Helpful Guy [New York Times]