I have white stuff on the back of my tongue and big bumps on the back of my tongue?

Examination. To play it safe, get it looked at. A white coating on the tongue is fairly common and the bumps you see may be the normal presence of large taste buds. Without seeing you, however, it is impossible to know if there is an issue requiring treatment. At the very least get a tongue scraper and see if it cleans up at all.
Tongue Scraper. Bumps are either circumvalate papillae-taste buds, or tonsil tissue. A tongue scraper is the best thing yet to help clean tongue--amazing (and kinda gross when you see it work!). Rinses are just ok. Like washing your car with spray from a hose, when dry, it's still dirty- you gotta scrub to clean- teeth too! if no relief, see your friendly neighborhood dentist.