Orient, who led League One for much of the season, have slipped four points off the automatic promotion pace following four games without a win.
The O's were beaten 1-0 at home to Bradford on Saturday, having been held to a 1-1 draw by Oldham in midweek, and Slade admits those dropped points are likely to prove costly at the end of the season.
"Is it about the play-offs now? It probably is," said Slade.
"It's so frustrating, the week we've just had. We might look back and kick ourselves.
"But in terms of effort and commitment I'm not sure we could have given much more in either of the games."