New noise not sure what it is

[littlebigrig6.0]

I noticed I am now getting a knocking noise when I apply my breaks, sometimes it happens when ever I break, sometimes its when I break hard, either way its getting louder, It feels like its coming from under the driver seat, but its a thump thump thump sound until I stop. I am also getting a little pulsating in the breaks. not sure if its related.