Well first it may be because you are using too much conditioner? You may think that since your hair has grown longer that you need more conditioner but the more conditioner you use the faster your hair will get greasy so use less. Also try not to use too much hair spray and try not to touch it alot during the day because the oils on your hands can make your hair greasy and maybe even try switching shampoos. Hope this helped.
Try to train your hair so that it only needs to be washed every other day. Washing your hair everyday strips it of it's natural oils, that will make it so that when you keep doing it, it will get oily faster. For the awkward in-between training stage, you'll just need to tough it out for a little while. Also, a good tip would be dry shampoo, or baby powder!