I would agree with your family and friends. Since you mention that the family doctor says he is fine, I am certain you have had his hearing tested. If your son understands what is being said to him, he is adequately handling the most complex part of language learning. If he should need therapy later on, it is a lot easier to deal with speech production than language comprehension.
Let me offer a few simple suggestions that might hasten his talking. Talk to him lovingly and frequently, making certain that the main things he hears from you are not criticism and scolding. When feasible, squat or kneel down and talk to him at eye level. And find time to read to him once or twice a day. Choose books that have a lot of pictures, and ask him questions such as, "Show me the doggie, kitty, shoe, car," etc. Then, a little later, point to a picture and ask him, "What is this? What do we call it?" If he comes even close to the right sound, compliment him and repeat it correctly. But be careful to avoid saying, "That's not the way to say that; say it like this." You want to make talking a source of pleasure, not anxiety.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.