Undecended testical, when should I be concerned?

[*Efjay*]

I got so many mixed opinions on this when Iain was born & I really am not sure who is right.
When Iain was born his testes undescended. They could be felt & the right one could be moved down.
But now, he is 4 months old. I am unsure that I can feel the left one & if I can its very small compared to the other side.
I have a Dr app in an hour but I want to have a bit of info up my sleeve so I know he knows what he is on about as the last time I seen him about it he seemed to think it would be fine & not to worry unless its still not come down when he hit puberty.....

Im thinking I will just ask for a referral to the pead