When is too early to contact Early Intervention? When is too late for a child's first word?

My son is 15 months old and will turn 16 months on the 17th of January. He had his last check up two weeks ago and has passed all his milestones and expected growth except for his verbal skills. He still babbles like crazy and only repeats sounds but no words. Everything is Dada or Ah or Hey and has been since August. The doctor said he wasn't too concerned but brought up Early Intervention and said if by March (18 months old) he still isn't talking I should contact them and how wonderful of a program they are. Of course, I've been concerned every since and the past 2 weeks we have been trying to repeat a lot of words like ball, cat, mommy daddy etc but still no interest. He said boys tend to talk later and since he is very social (he was babbling and interrupting the doctor the whole visit and playing with him haha) that he doesn't think he would end up on the spectrum but EI is a great program that would help us help him and find out if we need them. He said if before his 16 month visit I feel they should be contacted then by all means I can.I have spent the past 2 weeks a little worried and overanalyzing every little sound, gesture, and lack of words by son has been doing. Am I overthinking this? Anyone with Early Intervention experience suggest I contact them now or should does this seem like a normal thing? via /r/Parenting http://ift.tt/2hOXwq2