Can't wrap my brain around it

Hi, i was just wondering if anyone else feels like they won't believe it when they actually get pregnant? In 2nd month of trying ( well first month because got mireana out October 6, 2016. And had first real period November 4th.) and i really want to be pregnant by Christmas so i can tell my 5 year old he is going to be a big brother on Christmas day :)... And because me and my husband are so ready and excited for a second child. But i can't wrap my mind around the fact that i could be carring another one. When didn't try for our son it just happened.(happy suprise) and it took me until i was about 20 weeks to really realise i was a mom. Im excited but just wish i could wrap my mind around it...does any one else feel this way?