My baby isn’t rolling or crawling yet...

My dude is going to be 8 months old on the 31st. He sits unassisted perfectly and has been since about 5.5 months, but he never rolls back to belly and is just not very mobile. His neck strength seems fine to me, but he absolutely hates tummy time! He will either roll over onto his back and keep doing that until tummy time is over, or he will just put his head down on the ground and cry. I’ve tried distracting him with toys, songs, etc. but he just doesn’t seem motivated. Should I be worried? I’m thinking of bringing this up with the pediatrician, but I know every baby is different etc etc and he is hitting all other milestones...here’s a photo of my little booger