Delayed walking. A delayed condition?

Hi, My son is 15 months old. He is now walking with support. He tries to stand independently for 5 seconds and falls down. Actually at 9 months my son started sitting without support only when i make him sit. But he did not sit by himself till 11 months. He was only crawling on his tummy. So i gave to him practice how to sit from side lying position and he quickly picked up the nake and within a week he sat up by himself and also keeps pivoting in sitting position. Later he grabbed the chair stood by himself at 12 months and now walks by moving the chair. I took him to nearby pediatrician for general check up and delayed walking. She is referring us to a neurologist and take some tests as his current development is only 10 months old motor development and also says he sat independently very lately. She is recommending a physiotherapist for strengthening him. Please advise do i really need to visit a neurologist for this. Is my son at such a delayed condition? Please