Wayne Brown gave the Pirates a flying start, but Bournemouth launched a late fightback and were rewarded with goals from Mathieu Baudry and substitute player-coach Steve Fletcher in the 84th and 88th minutes.
Campbell said: "It would have been devastating if we had only managed a draw after leading for so long. To lose is even worse. Now we need to win our last two games to stay up and they're massive for us.
"But having said that I think we have a very good chance of staying up. I thought we were excellent from start to finish and created numerous chances for a second goal.
"I'm disappointed to have conceded a goal from a set-piece, but the way we played I felt we should have won comfortably.
"All the while we only got the one-goal advantage. We left ourselves open to a comeback like Bournemouth's. I hope we can learn from it. I felt we passed the ball around really well and if we can play like that for the next two games then I think we can survive."
Source: PA
Source: PA