Sorry not pleasant...
Could it be just stress? I know that usually this time of year I can be up to two weeks late and I think nothing of it just the change in weather is what does it for me. If you are concerned call your surgeon or PCP. Possably changing your diet could have had an effect on your cycle as well. I would at least call my pcp to put my mind at ease if I were you and then just relax. Hope you get some answers soon.