I totally agree with the first post. The whole point of what the Party has done is to get Winston (and the other people in the society) not to think. The Party wants automatons who have no real thoughts, who just do what it tells them to do.
To the extent that Winston is thinking anything, he would simply be thinking that whatever the Party does is right. He no longer has the capacity for individual thought.
I would doubt that he is "thinking" anything. His mind wanders a bit, but it is clear that he can no longer think when he reverts to what he has been taught, when he writes 2 + 2 = 5 on the table. The Winston who could once think, keep a journal that he says he knew would be the end of him, dream of a rebellion led by the Proles, the Winston who thought he would NEVER betray Julia --- that person is no more. He seems capable of sensoring his thoughts, but it's not really thinking --- it just his indoctrination kicking in.
The Winston who once hated Big Brother when he could think now loves Big Brother ... thinking is over.