Breastfeeding and periods?

Steph
My 5 month old son is ebf. I got my period back when he was two months old and they had been regular like clockwork. This month however I am 5 days late from my predicted start date with no signs of it happening anytime soon. I did take two pregnancy tests a couple of days apart with negative results on both. Is this normal for breatfeeding mommas to miss periods? Thanks everyone 😊