How long do it take to get lung cancer from smokin?

im 19, started smokin a lil bit at 13, than stopped at 15. started last august smokin about 5 a day, than upto 10 cigarettes a day, than in march afta loosin my job, a pack a day, n for da past 2 weeks since my break-up, im at almost 2 packs a day. i dnt c myself stoppin, n my friend told me my lungs r already black...is dat true?