David Healy struck in the 96th minute to spare the home side's blushes in Wednesday night's World Cup qualifier at Windsor Park, but O'Neill insists that his side should have taken more from the game.
"It was a very frustrating night and one of those games where it didn't seem to go for us," BBC Sport quotes him as saying. "From the moment they scored we dominated and should have won.
"To be fair the players went to the 96th minute and David popped up with an equaliser.
"We just have to keep doing what we're doing, keep believing in the players and working with them."
The result leaves winless Northern Ireland in fourth place in Group F with qualification looking like an insurmountable task. O'Neill has yet to secure his first win since taking charge of the national team.