Went to doc for throat he looked&said it was fine well I was looking & I saw many bumps in back like polyps kinda. How do ik if I have throat canc?

Unlikely it's cancer. There are normally 'bumps' at the base (back) of the tongue; they are called papillae, and are made of mainly lymph tissue with valleys and hills between them giving the bumpy appearance. Oral or throat cancer is painless, occurs almost always in smokers or heavy drinkers, and most commonly people that do both. The typical appearance is a white plaque, called leukoplakia. If any concern, c dentist.