Late period

I’m 2months pp almost 3 since my son will be 3 months on the 16th. I just barley noticed that my period is late by 3 days, I had it last month it was a normal period but it lasted very short only 4 days the last two days of it were just brown blood. Is this normal? I haven’t taken a pregnancy test yet, but I was wondering if any Mom’s have experienced this before? Does it just take awhile for your cycle to regulate? I’m also not breastfeeding I haven’t breastfed at all my son drinks formula so I know it shouldn’t be late from that. Please let me know if you’ve been through something similar or if this is just normal ☺️