I can't stop thinking about becoming a mother in the future and get on with being a teenager?

I am 17 and doing my ALevels at the moment so I should be concentrating on my work but also going out and having fun with my friends but i don't really want to. I'm not a recluse I love socialising and having occasional nights out. But all I can think about alot of the time is having children. I am not going to get pregnant now but I don't really have any ambition other than to be a mum and I feel broody all the time. Next year I'm going to be a primary school teacher because I love working with little kids and I get very attached to them. When I volunteered at preschools last summer I chose to do more hours there rather than go out with my friends. What shall I do? What do you think about what I said?