My hair has been so greasy lately?

Wash your hair every two days, or try to leave it longer as much as possible so it gets used to being left long. If you wash it everyday it washes the natural oils out your hair which keeps it healthy, otherwise like you say your hair goes greasy. Also it can be hormonal, but the above should help you anyway. Try dry shampoo spray this helps, and also putting your hair up it's hard to notice if it's greasy or not. I wouldn't worry too much, just try out what I said:)