On-loan striker Nathan Delfouneso was the match-winner for the Seasiders in stoppage time, after Thomas Ince had cancelled out James Henry's opener.
Jackett said: "I'm very frustrated and disappointed with both the goals defensively.
"Over a period of maybe 10 games we've given away too many goals with not enough clean sheets.
"We've given two goals away again. Every game we have not had zeros against us enough.
"You have to come through those periods of pressure and make sure you don't concede and we didn't do that well enough.
"I felt going forward we probably had more clear-cut chances than we have in a while without necessarily putting them away.
"It was tough from us to get a decision from the referee and the linesman throughout the game, but that's how it is for us away from home.
"It hurts the players and myself as manager to have lost four games on the spin. Whatever the details of the game are, there's a line there and that's winning and losing."