Baby doesn’t want to sleep on back

My son loves sleeping on his sides since he was about 3+ months old. If he wasn't sleeping on his side, with his pacifier in his mouth & legs hugging his pillows, he wouldn't be able to fall to sleep. Recently (6+ months), he likes sleeping on his tummy lately and I realized that he would sleep longer this way. Since he's a pro and turning and flipping, I wasn't too worried as long as his nose and mouth isn't covered.