First of all, I am sorry to hear that you are having to deal with oily facial skin. The best recommendation that I can give you is to set up an appointment to have a consultation with a dermatologist
to be evaluated. However with that being said, here is some information for you about oily skin. Skin has something called sebaceous glands that secrete oils that help moisturize your skin and keep it healthy. In people with oily skin the sebaceous glands are overactive and secrete more sebum (oil) than is normal. Accumulation of the sebum make the skin texture heavy and thick, resulting in a greasy or oily feeling. When not taken care of appropriately, this excess sebum can result in oily skin, blemishes, and comedos (pimples), and plugged pores (blackheads). On the upside, anecdotal evidence shows that patients that have excess oil on their skin tend to have less premature aging and wrinkling, which is a positive in the long run.
The causes for hypersecretory sebaceous glands is multifactorial. It can be related to genetics, diet, cosmetic products, hormones, pregnancy, and even behavior patterns. In general you can think of treating oily skin in two separate main categories; removing the excess oil, or decreasing the production of oil. I do recommend seeing a dermatologist for an evaluation and recommendations, because the sebum is present for a reason to keep your skin healthy, and if you remove too much, it can be detrimental to your skin, and also it can stimulate the secretion or even more sebum. It is not uncommon for hormonal changes during the teenage years to cause hyper-secretion of sebum, which typically normalizes with time and further hormonal changes. Hope this helps.