After his team made changes since the last race in Jeddah, the seven-time world champion said that the car felt the best it had ever felt at the start of FP1.
However, following set-up adjustments, he reported that it got "worse and worse", and that ultimately in FP2 he felt the "least confident" he has ever been with the car. He finished the session in 18th place.
"I obviously don't feel great," he said. "We had one of the worst sessions I've probably had for a long time.
"FP1 generally felt quite good, the car in FP1 run one felt the best it's ever felt.
"And it just got worse and worse. And then we made some big changes into FP2, and it was tough."
He added: "After that session, I feel the least confident I've ever felt with this car but there are positives from that FP1 run that we did."
Hamilton's team-mate George Russell had a better day, taking third spot in FP1 and sixth in FP2.
"I felt pretty comfortable out there from the beginning," he said. "We made some changes since Saudi and Bahrain, we're still trying to understand this car further.
"Every single lap is so valuable, you're learning more and more about it, and trying to get it into the sweet spot.
Source: Autosport