Pompey bounced back from two straight defeats at the end of September with a 3-0 league win over Rochdale and a 2-1 midweek victory at Oxford in the Johnstone's Paint Trophy.
They trailed to Conor Hourihane's early goal at Home Park on Saturday but Jed Wallace's third goal in four games secured a well-earned point.
Whittingham said: "We've had two wins and a draw in the space of a week and that's very pleasing for us.
"You set up to try to win the game, but I was happy that we were able to get back into it and then push on a bit in the second half.
"I thought the result was fair. We got the goal at the right time - scoring just before the break gave us a boost.
"I thought we were then the better side for the first 25 minutes of the second half before Plymouth came back towards the end."