Matchmaking Ban - Halo 4

I was banned from matchmaking on xbox LIVE but I have literally NO IDEA why? How can I find out why?

I haven’t quit a game, haven’t been cheating, this game is literally the reason I have xbox LIVE. UGH what do I do?

edit: I checked my service record, and for some reason I have 5 DNF’s listed. I don’t know how, I always finish games. Any idea how long the ban will be?

Perhaps disconnects counted as DNFs?