There are two steps to most treatment plans for Crohn's: Induction and Maintenance.
Induction is the initial phase of therapy to knock down the inflammation and get the disease under control. Steroids are usually used for that, although some biologics can also be used for induction. But steroids have a lot of side effects and thus are not a long-term solution. So sooner or later the doc will try to move you to a maintenance medicine.
Depending on the severity of your disease the doc may recommend an immunosuppressant drug such as azathioprine (brand: Imuran) or perhaps methotrexate. Or you may go directly to a biologic or he may prescribe both. A biologic is a human or humanized antibody that interrupts the immune response in some way, usually by attacking your tumor necrosis factor (TNF) of by blocking the activation or the target binding of your white blood cells. Biologics are complex proteins rather than small, simple molecules so they are administered either by injection or infusion.
Also available are the salicylate derivatives, but they are very mild drugs and are not very useful for Crohn's in the first place. They are better used for Ulcerative colitis. From your symptoms I suspect your disease is too severe for those drugs.
Good luck
