Are you thriving, physically? Are you recovering from workouts? Are you sleeping well? Is your mind sharp and focussed? Are you digesting your food properly? Is your diet balanced and consistent and nutritious? Do you eat lots of veggies and unrefined foods?
If you answered 'yes' to all of these questions, you've got your bases covered. Although I still think some basic mineral, antioxidant and fatty acid supplements can be beneficial for most people.
Some naturopathic doctors and chiropractors have nutritional profile sheets you can fill out to find out if you're eating the right variety of foods to cover all your nutritional needs. If you really want to get serious about good nutrition, talk to a naturopathic doctor - I'd recommend that over seeing a dietician or nutritionist any day (they pretty much stick to the highly outdated 'food guide' and you can get basic info like that for free anywhere).