Chris Brown put Doncaster ahead in the first half, but although Portsmouth seldom posed a threat, when the chances came the home side's way they failed to take them.
Doncaster took their foot off the gas and Portsmouth cashed in when Jed Wallace fired home a left-footed shot from 10 yards after Patrick Agyemang had set up the chance.
Whittingham said: "We are not too euphoric because it is a draw and not a win - whether we deserved to win is immaterial.
"Our results have been better recently, but it's been building for some time.
"Everyone knows the problems we've had with players coming and going, but the lads who are here now have worked really hard.
"The results we have been getting is a reward for that and it's very encouraging to see players with a spring in their step again.
"I don't think they dominated too much, we allowed them to play their game in the first half and put that right after the interval.
"All I said at half-time was really to point out that we were only a goal down against the league leaders and still in the game."