every baby is different. different strengths and weaknesses. my girl was a 36-weeker and ahead of all milestones, BUT only when she wanted to. (eg talks clearly but only to me and my mother, could walk at 9 months but wouldnt then morning after 1st bday party she was walking non-stop. even now will only talk at home, not out and about. can say her number and some letters and is bilingual but only if she wants to or sees a purpose to it. BUT she wont repeat what we say when we say it.) if you're concerned talk to paediatrician to be safe, but if you're comfortable then just work on the milestones LO is responding to for a start
I think because he was born at 32 weeks they are on a different developmental curve. My baby was born at 37 weeks due to pre eclampsia but I notice he hit the milestones more towards the end of month.