That reminds me of a commmon experience I have with asperger's. English is my native language, and yet I regularly have the issue with words not actually coming from where my thoughts are generated, and I can't always express the thought I've had as quickly and fully as I would like.

More recently, I've been taking a foreign language, and it feels much the same only more extreme. Since I've actually lived in the country where thins language is spoken, my words come at a reasonable speed now and feel automatic. The gap between thought and words is larger than ever. (2 years into the foreign language vs. a lifetime with my native should do that though)

I wonder if people living with Asperger's or similar disorders that delay development of language result in every language being your second. :P