Has anybody not known they were pregnant?

So my daughter is almost 2 now but ive always thought this was kinda weird... she is my 4th kid so you would imagine id have picked up the signs earlier? I had given birth to my 3rd child, Evie, in February 2015. I got my periods every 28 days as I always did and it was always regular as i didnt breastfeed. I had clots and all, lasting the full 5 days. It was literally THE SAME as my periods. I had no reason to believe I was pregnant. A few months later I took a digital cause I didn't want it to go to waste nd expire lol i randomly found it in my bathroom. It was positive 3+. Went to dr who did bloods, asked when my period was and it was 4 weeks prior so i assumed I was a month, the bloods didn't add up he thought it was a molar... had a scan and there she was sucking her thumb on the scan... A few weeks later periods stopped, never had a low placenta or anything that could explain the bleeding, ended up enormous with heartburn and she was 9lb 12oz.... its so weird cause i could have gone even furthe not knowing r had it not been for the test. anyone else experienced that?