My period might be late...?

So in the last year my cycle has ranged from 28 days to 33 days long. 30 days has occured most often and only 33 days once. I do not take any hormonal birth control and have been having unprotected with a man who has told me he had a vasectomy 5 years ago. Today is day 31 of my cycle and no sign of a period yet. Should I be concerned yet?