Late Period

Hey all, so I am trying to figure out what I should do. I had my baby girl in October and had my first period past partum December 6th, my second January 1st. The app is showing I should have started my period yesterday and it's still not here. I'm trying to figure out if I should be taking a test or how long I should wait before I do. I've been cramping, I've been moody and having all the normal symptoms, just no period yet. Can it be normal for them to not be regular yet or should I set a day to take a test?