Has anyone dealt with speech delays?

DS will be 18 months old in a week and a half. We went to the doctor yesterday for a follow up sick visit and I asked about DS's speech. He babbles constantly but only says a handful of words. Previously, we were told that sign language counts but his new pediatrician disagrees. He also said mama & daddy don't count. That gives us a grand total of 5 words...if that. The doctors wants DS to have 7-20 words with two 2-word combinations by his 18 month appt (in two weeks!). I'm just sad and worried. DS was ahead on all of his other milestones so I wasn't really prepared for this. I could really use some advice.