This is a good question.
You'd be best served to complete your cycle and save the Tren. Even though you only have three weeks under your belt there are possible 19-Nor prolac/progest complications when combining these two particular compounds. For more on this see the last paragraph of the NPP profile.
Now, should you elect to go AMA (Against Medical Advice...namely mine), be sure to find an accurate account of NPP's half-life and observe it for 8-9x, before switching. This will negate their interactions, but may also be inconsistent with your planned cycle duration as its already 1/4 over.
Sometimes its just better to stay the course!!!