no it wasn't a period for october or you on any contraception? Or had unprotected sex
There are numerous reasons for having irregular periods. High level of stress, cholesterol, hormonal imbalance, chain smoking, dramatic changes in your life style may be some of the common causes of you irregular periods.
If this was the first episode of irregularity in the periods, then wait for the coming cycle and try lifestyle modification by reducing stress and decreasing cholesterol levels. But if the repeat happens, then pls consult a gynecologist and get yourself thoroughly examined to diagnose the cause of irregular periods and start with the treatment.
I hope it helps. Take care and regards.