You do not need your mom for birth control, you can get it without her consent, and for free possibly.
Planned parenthood usually offers teens low cost and free services, so does your local county 'health department'.
Parents will often not want to think about their daughters having sex, but it is going to happen.
Your b/f may want baby, but prenatal care and having a baby is upwards of 10-20,000$. I doubt at 16-18 he has that kind of money.
You may need to just get on bc by yourself.