Combination can be the most frustrating type of skin to have. Usually oily on the t-zone (forehead, nose and chin), and dry across the cheeks.
Sometimes combination skin can just be down to genetics. But it's always worth considering that it may be your skin care routine which can aggravate the condition. Switch to a gentle cleanser which won't strip your skin, and use a moisturiser which is designed for combination skin. You're looking for something that will hydrate your dry areas, but that won't clog pores.