i planted tree about 6 years ago, bloomed for 3 year then stopped. how do i get it to bloom again.

From my experience there are usually three things that can affect flowering on most trees and shrubs. Amount of sunlight, fertilization or the lack of it and improper pruning. I would imagine the improper pruning does not apply, so it is probably one of the other two. Is your tree in the shade? Is it otherwise healthy looking? Or is it yellowing or losing leaves?

we moved in this house about 3 years ago and have a white dogwood on the side. it's flowers were pretty sparse so last year i climbed up there with a hand saw and pruned away. this spring there were TONS of flowers! maybe it would help you too. i haven't fertilized but maybe will this year.