The seven-time world champion endured a hugely frustrating Emilia Romagna Grand Prix, as he was left a "sitting duck" when he got trapped in a DRS train and ended up a lowly 13th.
After the race, team boss Toto Wolff apologised to Hamilton over team radio for being given an "undriveable" car.
Hamilton's title chances now look incredibly slim and, after being lapped by race winner Max Verstappen at one point, Mercedes even faces an uphill challenge to get itself back in the hunt for wins.
Asked about his level of frustration when he has been so used to battling for victories in the turbo hybrid era, Hamilton said: "It's been difficult and it's definitely not easy, but we all feel it as a team.
"And at least George [Russell] got some points today for the team. So apologies to everyone that I wasn't able to do so."
Mercedes maintains faith that it can get on top of the porpoising problems that are holding it back, and says everyone is pushing hard to get to the bottom of what is going wrong.
"I think the team is... as I said, everyone is feeling it and everyone is head down, trying their best," he said.
"So there's no one that's giving up and everyone is just trying to move forward as fast as they can."
Hamilton said he was pushing as hard as he could to try to make progress up the order, but was powerless to find a way past the AlphaTauri of Pierre Gasly who was ahead of him for much of the afternoon.
"I really found it frustrating and I just wanted to move forwards," he said. "I just wasn't close enough to overtake. I was just a bit of a sitting duck today."
While Mercedes works on car developments that it hopes can help it overcome its issues, Hamilton said that he was not expecting any dramatic change of fortunes before the next race in Miami.
Asked if he was looking forward to the new track, he said: "I can't say that I'm particularly looking forward to it at the moment, but I'm sure during the week I'll get to a positive frame of mind.
"I'll be at the factory tomorrow to work with the guys to see what we can improve."
