I had a similar thing with DS. He is/was a very late talker and has had a lot of speech therapy (he was barely talking at 3, his first ST lesson his word for "bubble" was just a "b" sound. At 4 he had improved but still didn't have the verbal skills to tell me who he wanted to invite to his party.) On a GP advice we had him assessed for autism due to his speech delay, lack of eye contact, he doesn't like loud sounds (during Wiggles and Playschool concerts he sits with his hands over his ears) and he doesn't read facial expressions very well). The ST also bought it up and suggested a second opinion which we got. So far we've had 3 paed assessments, all of which have come back as fine, however, 2 have said he is borderline to warrant further investigation but we shall see how his progress goes in the next few months.