Post Partum Period

Hey guys, is it normal for your period to come back one month but not the next month?

I haven't had a period since March of 2017 lol got pregnant April 2017, had baby Jan 2018 and got a first time period March 2019. It was around the 4th of March so I assumed it started up again and I'd get it again this month but it hasn't shown yet. I did have unprotected sex around ovulation time, according to the app but idk if I was ovulating for sure because I just got my period.

Any similar stories or help would be great!