Journal your food and workouts to keep closer tabs on calories that you take in and the calories that you burn. You might find that you are eating more than you realized or not working out as much as you think. Or you could be eating too little, causing your body to go into starvation mode. Once you have the results from your journal, if you don't find anything off, ask again with more details.

I'm no expert, but I do know that if you want to burn fat/lose weight you need to burn more calories a day than you take in. You could just be balanced right now so you're only maintaining. Maybe cut back yoru calorie intake and increase your work out time? Just a suggestion.