The fact that you said A was done means you are now caught in a lie.
And there is no way you can ever admit to that professionally. So now you are doing A and B at the same time. And A is blowing out by a lot. You over-engineered it. You had a zero productivity day. You'll pick up some small easy tasks to show some progress and maintain your reputation, but A is still not delivered, and now B seems like it took too long. ADD and procrastination don't help. And you are on probation. So now you are "almost ready to push B", but A is not done, and B is not done.
You've basically created your own ponzi scheme (and the stress that goes along with it) from never wanting to admit that you have a couple days where you weren't productive, and that you felt a task shouldn't take as long as it should.
Anyone?
Ask your team lead for help