Knee pain is now swelling up a month ago it felt like what a sprained ankle felt like except it's in the back and lower part of my knee. This morning it swelled up. What can I do about pain and swelling? By the way I have cerebral palsy and possible art

Bakers cyst.? If you have a swelling in back of your knee, it isa very common place for a cyst to form. See your orthopedist for evaluation and treatment.
Get re-evaluated. Pain could be as a result of many different things. One would need to do a thorough history and physical exam and possibly sometimes laboratory and radiology exams to determine the exact cause. Have it re-evaluated and voice your concerns.
Have . Have this evaluated by an orthopedist. You may require a knee aspiration not only for pain relief but also for fluid analysis. This will differentiate between an infectious vs. An arthritic process. Crystal analysis may even be able to establish the proper diagnosis. The doctor will require x-rays and may order additional testing.