Its good that your living with your boyfriend and in a relationship, but you are young, i got pregnant at 16. and now have a 17 week old baby girl, she wasnt planned.
You should stop stressing about wanting a baby, as this can make it harder to become pregnant, just relax and enjoy the sex and if it happens it happens.
i hope you understand what bringing up a baby is like, and that they depend on you 100%.
Good luck. x