The last Taz in Y.D. siman 18, based on the Rash, writes that even though a Talmid Chochom is generally believed to paskin for himself, he is not believed when there is a chezkas issur, a previous status of prohibition. The animal was prohibited to eat while it was alive, and therefore the shochet is not relied upon to paskin for himself in this situation.
However, with regards to slaughtering for himself if no questions arise, there is a principle that רוב מצויין אצל שחיטה מומחין, most of those doing shechita are experts, and he is therefore allowed to shecht his own dinner.
The Chayei Adam klal aleph se'if 10 accepts this Taz.