The former Brighton & Hove Albion striker hit the bar in Burnley's 3-1 defeat to West Ham United on Saturday.
"I can't buy a goal at the moment," Barnes told the Burnley Express. "I've hit the bar, deflections, it's just not dropping for us. Anyone else that normally hits the bar, it hits the keeper and goes in.
"We've just got to keep going, regroup and get ready for the next one. For the strikers it's frustrating because we haven't scored since last season but it will come, I'm sure.
"Of course, without a doubt, we believe in our own ability and if you didn't, what would be the point of being here? We're in the Premier League, it's fantastic so we've got to believe. I can cope at this level for sure."
Burnley sit 19th in the table following the defeat.