I hope this does not sound like a stupid question.How would i know if i had cancer of the spine?

The reason i ask is i have got lower back pain i have had this pain on and off for a while.The last couple of days i have been feeling quessy in the stomach and i feel giddy and i feel like i have pressure in the head.I know this must sound silly but i suffer anxiety really bad and my anxiety is that im dying.I know there is probably nothing wrong but i wanted to get some veiws.