I am not the most productive writer I know, so take my advice with a grain of salt. I think that when you're feeling burnt out or uncreative, the first thing to do is to take care of yourself. Sit on the couch all afternoon and read a book (OK, so I could do that before I had a kid! No more.) Eat better food. Take leisurely walks, either in the woods, on the beach, or in town browsing through fun stores. Get enough sleep.
Another approach is to switch genres. Try a few random writing exercises or prompts to get yourself going. Write about someone else. Write a short story, or a poem, if you normally do longer fiction or non-fiction.
Finally, hang in there! These things ebb and flow.