Periods after pregnancy?

i had my baby 14 weeks ago, but ran out of breastmilk around 8 weeks so my baby is bottled feed within two weeks of stopping breastfeeding i got my first period. 28 days later i went to the bathroom and wiped and there was blood and i assumed it was the start of my period... but nothing else for the rest of the day came, the next day when i had abit of blood on the loo paper but again nothing more. It has now been 7 days since it was due and i have had nothing. is this normal for periods to be irregulaur? I dont get why there was a small amount of blood on the loo paper twice.