Try playing the F chord shape higher on the fret board where the strings are closer to the frets. For example, play the chord at the 10th fret. Now, you're actually playing a D chord. If everything sounds fine, move the chord to the 9th fret. Still sound good? Continue moving down until the chord doesn't sound good. Work at that fret to get it to sound right and then start moving down again.

Playing chords that contain barres are difficult in the lower positions. Starting higher and moving down allows you to slowly build up your strength.