He's clearly lacking confidence in his finishing. I've said before he looked to be mentally weak before in the Bundesliga as well, where he would go on long streaks without scoring (though this season is much longer than he's ever had).
I think the most difficult part of the EPL for him has been the pressure on him, along with the scrutiny, which he wouldn't get playing for Leipzeg. He's making as many chances for himself as he did in the BL, the only difference is that he's completely missing them.
Previously, the one moment where you can say he did have heavy expectations on him was the 2018 WC, which he went into in fine form for Germany, but he again lost his finishing touch there.
A season break would be the best for him. This season has been continous in it's games with no break at all, maybe a summer break can help him get his head back and find his scoring touch. Although if Chelsea sign a new striker then would there be any opportunity for him to find it again?