Blocks reappearing after mined

after i mine leaves or trees they immediately reappear, I'm nowhere near my spawn point I'm not on multiplayer or a sever, I'm using a mac computer so playing with files is limited or i just don't know how I've discover it to happier when I'm mining to, i used to be able to dig to bed rock with a stair set to top as well as a jungle tree climb all done in 40 mins now it takes over 2 and a half hours,