Villa have lost all five games they have played since then, and have not scored a goal in any of those games.
"I never think fireproof, I never think anybody's bomb-proof," Lambert said.
"I know football is about trying to get results. It's got nothing to do with my contract. We've just not clicked."
Villa have now played more than eight hours of football since their last Premier League goal, following their 2-0 defeat by QPR on Monday.
But Lambert thinks his team can address that, starting with their home game against Tottenham on Sunday.
"We've got lots of players who can score goals," Lambert said. "You've just got to stick with it and keep the belief."
According to the BBC's West Midlands reporter Richard Wilford:
"Although Paul Lambert is held in very high regard by Villa owner Randy Lerner, he is acutely aware that results have to improve in pretty short order. Since signing his new four-year contract on 17 September, he has seen his team suffer five successive defeats, failing to score in any of those games.
"With the club's supporters increasingly vocal in their criticism of Lambert's playing style, and attendances at Villa Park suffering, it is not unreasonable for Lambert to feel he is not 'bomb-proof'. As loyal as Lerner seems eager to be, the next three games against Tottenham, West Ham and Southampton cannot see Villa continue this barren run without Lambert's future being open to debate."