Since you already have had bleeding after a gap of 2 months it is not pregnancy
. You have not mentioned your age. Assuming that you are approaching menopause
this is a common occurence in premenstrual age. And again assuming that you are not approaching menopause it may happen some time that one skips a period, reasons may vary from stress
physical or mental or maybe an indisposition. But if it becomes a regular occurence or if the bleeding is too much then i guess you should consult your gynaecologist in person. But for a single instance, and not very severe bleeding (of course since a month was skipped the unshed endometrium for 2 months may appear as large blood clots
and bleeding may appear to be more than normal) you need not worry.
hope my answer helped you.