If it weren't for the word lately, the choice would simply depend on what exactly we've noticed. For simplicity we'll ignore the negation and suppose we noticed one of...
1: you have been doing it
you were doing it before, and you're still doing it now
2: you are doing it
you're doing it now, but maybe you weren't before
3: you were doing it
you were doing it before, but maybe you're not doing it now
4: you had been doing it
you were doing it before, but [probably] you're not still doing it now
But lately implies from some [relatively recent] time in the past up to and including the present, which means that only #1 works really well. The others are at least "credible" (though #4 seems rather strange to me - why introduce such a complex verb form when there's nothing that definitely needs to be identified as having happened before something else?).