Hello, @seacliff – I agree with @astaingegerdm that requesting an evaluation might bring clarity. My oldest had this done, as he was on the delayed end of sitting up. I can't recall for sure, but I believe our pediatrician made a referral to the school district, who then sent out paperwork and then evaluators. In his case, PT and OT ended up working with him for over a year at our home and were very helpful.
Have you had the chance to speak to your pediatrician about your concerns? If so, what did he or she say?