I've been on yaz (drospirenone and ethinyl estradiol) bcp for over a Year my period is always light this month it's so heavy lasting 5 days now I have never missed a pill and not preg?

May be normal. Yaz (drospirenone and ethinyl estradiol) is one of the low dose pills and usually does cause periods to be short and light. This one heavy period could be due to some extra estrogen exposure in your diet, other drugs, or bthe enviroment. Infections and cervical problems usually cause bleeding at times other than your period rather than heavier periods.Hope this helps.