I'm not sure if this is what you want, but I think that you have connected the led and the pot wrong.
Now It's like this, if I'm not wrong:
The led is in parallel with the second part of the potentiometer.
But the potentiometer should come first (only two legs), limiting the current, and then the led.
Besides that, if the led drops 3.4V, you can't power it properly with 3.3V minus the voltage drop of the pontentiometer, it will be too dim.
And better use a separated power source for the led.
You should draw an schematic, decide how to connect and power it, and do the calculations for the current. For the max and min resistance of the pot. And maybe add a series resistor for the case when the pot is close to zero, to limit the maximum current.