ttc while breastfeeding

Me and my husband are ttc after having our second baby. I am still breastfeeding my 9 month old but with her eating more food I ended up starting my period. Now since I haven't had my period in 18 months how do I go about recording how many days my cycle is? My period literally started the 1st of January and lasted 5 days. I recording my ovulation days and now it says my period is late. But could it be that my cycle just is longer?