I just need advice not judgement

So recently my boyfriend and I of 4 months (I’ve known him for 1 year) but recently for the last the 2 months of us dating we talked about having children.. and we were 100% that’s this what we both wanted but Saturday night he may or may have not came in me and tonight he did for sure.. he’s super happy like excited and like I want this but I’m scared because I feel it’s so soon and we’re only 21 and 22.. and like our relationship is solid we were fwb for a solid year and finally made it official.. I just need to know if I should take a plan b or just let my life fall into place. Like I love him to the moon and back and reassures me that he wouldn’t go but at the same time.. honestly help, I want a family but I’m just scared. Please don’t judge me