Watching a baby and having a baby are two entirely different things. Your cousing goes home. You don't pay for it's diapers, formula, clothing, medical bills and other needs. You would also hoave no time for friends, parties, dates etc for some time to come.

At 17 I highly doubt you are realdy for a baby. Live your life. Enjoy your relationship with your boyfriend while you can before a screaming child begins to interupt your every waking (and non-waking) moment.