If you have no means of supporting a baby and you "think" your boyfriend may have a good job (come on, how good of a job can a teen boy really have? Good enough to pay for everything a baby needs???) but you're 17. You have no job. You have no car of your own. You have no house of your own. And you "hope" your parents will pay for the baby. Because you "want" a baby. Get a puppy, darlin' because based on your posts, you're not ready no matter what you say.
And no, you will not show as early as 4 weeks. You won't show until at least 4 or 5 months (16-20 weeks) with a first pregnancy.