Is ok or not ok for baby to sleep on tummy

Hi all. I'm a new dad here. My baby is 4 months 16 days old. 2 weeks ago he start to roll onto his tummy while he is in deep sleep. My wife and I have read online and it is strongly not recommended. He is currently able to roll onto his tummy on his own and able to lift his head firmly on his own. He is still not able to roll back onto his back. So we have been taking shifts to watch over him at night. Flipping him back to his back whenever he flips to his tummy. I personally hate this as it pains me to disrupt his sleep and sometimes he will whine and feels uncomfortable when he is not allow to sleep on his tummy. Need some help here. #firstbaby #1stTimeDad #tummysleeping