My 2 years 4 months old son does not talk,have heard him saying mama,nana but he says it like that not to me.For the past 4 months I have put him in early intervention speech therapy program but since then he has shown slight improvement.They are teaching him sign language in which he gets confused too like he does the sign for cookie when he wants juice otherwise he understand simple commands like pick up and give me.His eye contact is very fleeting,he looks at me when I sing songs for him otherwise he does not look when his name is being called or so.He does a lot of babbling but no talking.please suggest.

Have you had him tested for developmental and hearing issues?
There are a lot of posts here on the children board in relationships that deal with toddlers not speaking. Your child sounds like he may have a medical issue though. What all have they ruled out and what are they saying they think?