3 years old and still not walking unaided

Hi everyone just looking to see if there’s anybody in the same boat or anyone who has been. My son is 3 years old he was born 8 weeks prem started sitting and crawling quite late he’s taken his first steps , cruises and will walk with help but it’s like he can’t do it on his own he’s under the physio and she keeps telling me nothings wrong and I’m getting worried as he goes to nursery in September x