My problem has been the opposite -- I used to be on a 28 day cycle but since LCing it's gone to 26 (yeah, it's a great month when I happen to have a period twice! ugh!).

Are you exercising a lot, maybe? If I remember high school health class correctly, if you don't have enough body fat and/or are exercising strenuously then you can experience amenorrhea (loss of period).