Charlton had taken an early lead through Sordell before Fortune and Gomez goals at the death turned the game on its head for the Latics.
Speaking after the game Powell said: "It's tough to take. It was such a brave performance, we put our bodies on the line.
"Being 1-0 up for so long, and having put in a performance that was so committed and diligent, it looked like it was going to be our day.
"When it gets to that stage of the game, you're looking to just see it out. Sadly it wasn't to be. And it's the way it's going for us at the moment.
"It hurts. My dressing room is hurting, and so are the supporters. But we've got to remain steadfast and we've got to remain together, because that is the only way forward."