Wait until you are 21 and if you still want to do it then fair enough but put it to the back of your mind until then, spend the next few years gaining more qualifications, set up your own business, go travelling, write a book, make lots of friends, have some FREEDOM.
I had my dd1 at 17, I was single mum, it was incredibly hard work and tiring, my dd1 is nearly 11 now and the thing I regret is that I have NEVER had any freedom to do what I want, only once in my life have I been able to walk into a shop and pick a whole outfit without looking at the prices. I wasn't able to go out anywhere on my own without having to get a babysitter. I haven't been able to go travelling, I don't get many holidays because I can't afford them. Dinner has to be on the table at 5pm everyday and has been for as long as I can remember.
They say children get easier as they get older but I wouldn't say it is easier I'd say it's different, you need to think about the long term, it's not just the first few years that are tough.
To be a Mum you must.......
work 24/7 for no pay, no holiday days, no sick days, you must be a teacher, nurse, speech therapist, cook, cleaner, snot and bum wiper, you must never tire of their chatter or when they ask why why why why why why why why why why but whhhhhhhhyyyyyyyyyyyyyyyyyyy? what are cows made of? what is glass made of? who made the moon? why do we have 2 hands? you must hold your nerve when they are tantruming very loudly in public, you must not get embarrassed when they shout at the top of their voice why is that lady fat with a beard?
Why don't you become a childminder or a nanny until you are in a stable secure relationship?