You need to consult a speech language pathologist/ speech therapist about this. A speech language therapist is a professional who is specialized in childhood speech and language development. He/ she will be able to map the child's development so far and also diagnose problems, if any. They will be guiding you through the treatment process as well.
Rather than waiting any longer please take their opinion as soon as possible. In case there is no problem you'll come to know that and if there is a problem early treatment will benefit your child to cope up with any delay and come to the normal developmental course as soon as possible.