Clipping
It sounds like you are clipping all over the place (when the meter redlines and sound gets chopped and slashed up) Be more careful with your levels , bring the whole thing down if need be, and maybe compress some things to fit them in better if u want.
But the clipping leaves a lot of undesireable unclean artifacts. Thats all I haz to say :)
Thats definately the biggest issue this song has right now.