What Causes Periods Irregularity, Lateness, Spotting, Sometimes With Heavier Bleeding And Cramping?

I am 29y/o female complaining of irregualr periods. It started last month, my period was 1 week late, and when it came on i spotted for 7 days. Then my period came back on 2weeks later now i'm bleeding heavier than usual and cramping really bad than normal. My period has always been on time, i'm not on any birth control, i am sexual active with my husband, not taking any medications.