Alexander, whose side extended their winless run to four games in League Two, had been hoping to reignite a play-off charge at Adams Park but it was Anthony Stewart who had the last laugh with the only goal late on.
"There were some good performances but I can't be pleased with the result," he said.
"We've hit a four game patch which has gone the other way. It can change in a moment but we have to make it change and we can't wait for it to happen.
"We're still in the hunt and we're still in touch and that's what everyone here is aiming for.
"We've lost players through injury and suspension in the last few games and it's disappointing and it's something that we have to address.
"We wanted to win the game but we were undone by a corner. We can't seem to get a settled side at the moment and I think it's culminated in a couple of bad results."