Hi I'm not sure that I know the answer but if your recent smears were OK then cancer is possibly a no, when you say you have brown discharge 10 days after period was it a follow on or how many days in between, could be your heading for the change, I would go and see your Dr just for reassurance, the right sided pain and into leg with back pain could be something simple like sciatica but you do need to go and discuss this with your GP not because its bad but because he has the answer's which will put your mind at rest.
Also how olds your mattresses