Daniel Sturridge's superb hat-trick inspired Liverpool to all three points as they came from behind to cancel out Dimitar Berbatov's opener.
It was Fulham's fourth successive defeat at Craven Cottage and means they are still not mathematically safe from relegation.
Despite the defeat Jol was happy with the effort his side put in against Liverpool, feeling their opponents took advantage of their vulnerability.
"We were very happy to be on 40 points but we haven't been able to get a result since to be on 46 or 47," said Jol.
"If you look at the effort we've put in against Chelsea, Arsenal and even today, there's nothing wrong with the effort or application or mentality, but when we've needed to change the game to score, we've looked a bit vulnerable."
Jol conceded Fulham need to bolster their squad next season if they are to avoid struggling at the wrong end of the table, feeling they do not have enough goals in the current side.
"We need four, five or six players but that's normal at any club," added Jol. "We need to strengthen.
"Our home form was always good last year. Last year we could score out of nothing; we had Clint Dempsey to score winners. With Dimitar Berbatov, we gained somebody who could score goals but we lost things in other areas.
"Last season, we made a big step. We played fantastic football, especially after Christmas. But we had to start again. So we have to count our blessings that we had 40 points at the start of April."