Hi, unfortunately, this is very common. A lady can go for almost a year without a period, then bang, there it is again, this can go on for a few years before you completely go through menopause, that is why many women end up getting pregnant during that time, they think they are thru with that part of their life, so, they stop contraception, then all of sudden they find they are pregnant.
Hey specialmom. It doesn't seem to be all that unusual. Sorry you have to start counting all over again. :(