Keep the lines of cummmmunication open.
He needs to express himself better and should be encouraging you rather than just saying"You give lousy head"
If he isnt very verbal I suggest reading LoveDivas or Sharniquas threads on how they do it......They both offer wonderful tips

If you love doing it, you partner can tell...
( an hour or more? Sharniqua and Diva? Damnnnnnn........)

Have fun and remember.....nothing beats
PRACTICE PRACTICE PRACTICE

Peace out