Help Sitting Up

My son will be 7 months tomorrow and still can’t sit up on his own. He can’t even do the tripod sit which his pediatrician was concerned about at his 6 month appt but just told me to keep working with him.

I’ve tried using is boppy to help prop him up and pillows or blankets bunched around him. I try and just hold him lightly and let him try himself but he still can’t do it. It seems like every baby I know that’s around his age, even younger, can sit up by themselves and I know it’s different for every baby but he also shows no interest in crawling and can’t even push himself up on his arms yet either.

Anyone else deal with something similar and have any tips or suggestions?