Cant put weight on my knees.?

I have had cracking sound in my knees when i bend them for about ten years now. I am 25. but when my son was born in January 2011 I started to have constant severe arthritic pain in my right knee. and both knees hurt so bad and are so weak when i walk up steps or kneel down that i literally have to stop and rest or have help to get up. the only thing that helps are my husbands anti inflammatory meds. but i would say that my knees are in constant pain. mostly the right one. anyone know what could be wrong?