Birth control

Alena • I`m 18 I`m alena
When should I get checked out about my knee I went to the doctors they didn't do anything the arthritis cream didn't do anything Ibprohen pills didnt work so is it possible that I do have a blood clot from the birth control pills 
When I walk it's painful I limb 
When I sit down I can feel the pain in my knee 
So what should I do now?