Autism or just speech delay....?

Thanks Mamaof3!
yes he was evaluated by speech pathologist.... my son has been in day care since he was 5 months old, at 10 month of age he was moved to waddler room from infants because he was very mobile compared to other children so he ended up with children 4-5 months older than him....
he does play with them, its just when the speech pathologist came they took him another room and he just didnt want to be there.... came back and tehy gave him some toys i think and whenever he has new toys he is way too much into them, that can be the reason he wasnt playing with other kids, and i think they wanted to see more of it... although she did say that at one point one of the kids was upset and he went and gave him a hug!
then she tells me that she saw him as too quite compared to other kids.... i dont know what to make of it.... i guess i will go to the speech therapy route, get a hearing test done, and see if that makes any difference before i go to other route....
spoke to my pediatrician this week and he said he was NOT convinced at all that my son has any problems, and according to him language was something that varies greatly for 18 month olds... some talk very well and some dont at all.... and he seemed to be on the not all category but they usually pick it up.....
I know you had experience with this, I am curious to know how you knew? or at what time you found out?

Thanks,

Sanna