What makes you want to get pregnant?

I am 19 years old and have been with a guy for about 2 years… before we were together I never wanted kids simply because I wanted to enjoy my life to the fullest but recently I have wanted more and more to be a mom… and I don’t know why… and I mean the whole thing… the pregnancy… everything… and I don’t know why… the feeling grows stronger and stronger… I haven’t told my boyfriend partially because I don’t want to freak him out but mostly because he wants kids more than anything in the world and might go along with it… and we’re not financially stable enough to go through with such plans… but my question is why do I feel this way? Is it chemical? hormonal? psychological? ??? I have recently been a toddler teacher and am now a coach/counselor and am pretty much around kids 24/7 and my mom JUST had a baby girl… does this have anything to do with it? I dunno… just wondering and also if there’s anything that I can do to stop that… and don’t say teach kids or stay with an infant for a week or anything like that because I’ve been there done that… I’ve even taught swim lessons to infants to 15 years old so yeah… I get the idea… but thanks for your time! =D