2001 firebird it cranks but won't start

I have a 2001 firebird . Last night when I
got home I had even thought to my self
that the car had even ran better than it had
been . But when I went to start it this
morning it wouldn't start .It would turn over
but wouldn't start .
Note : a couple days prior to this . . . When
I would go to start the car , it acted like the
battery  was almost dead would barley  
turn the car over  . And this morning when
it wouldnt start . It sounded like it had a
brand new battery  . It sounded strong . But
won't start.