You have: Oily hair
You need: Dry or oil-absorbing shampoo. Avoid wax and pomade, as high-shine products only highlight the problem.
You should try: Apotheke Charcoal Shampoo ($27, ronrobinson.com) uses natural charcoal to balance your scalp's oil production and remove impurities from your hair. Percy & Reed Dry Shampoo ($22, us.asos.com) is a light spray used between washes that absorbs excess oil, giving your hair a cleaner look (even if you haven't showered in a couple days).
Expert tip: If you've been using your girlfriend's products, you're not helping your cause: On average, men's scalps produce twice the amount of oil as women's, so if your hair is extra-greasy, her shampoo won't be able to keep up.