I am experiencing early menstruation. its happened twice in a row. i was on a 14 day cycle and now im on an 18 day cycle. is this normal?

That seems too short: Many women have occasional variation of their menstrual cramps, mucus discharge, some spotting between periods, a heavier period, a lighter period, or even a missed period. Having one of these symptoms doesn’t necessarily mean there is a medical problem, but a visit to one’s Ob-Gyn doctor is helpful if symptoms are unusual... such as 14-day or 18-day cycles. Both are quite abnormally short.