I'm sure you think you're very mature, but surely the more mature thing would be to try living with your boyfriend and see if you actually get along as co-habitants? Rather than doing it under the stress of pregnancy and newborn days, which believe me puts the most solid, established, mature relationship under a serious amount of strain.
You sound incredibly naive about what is involved with parenting and raising a child. Have you started taking folic acid? Can you provide for a baby? Has your boyfriend offered a commitment to you and any future child that would outlast anything that might happen in your relationship?
Yes, you've had unprotected sex, you could fall pregnant (it wouldn't happen for several days). If it doesn't happen, please please sit down and have a rational discussion with your boyfriend about budgeting, living together, your career plans, his career plans, who would be a stay at home parent, how you believe you want to raise any children, what your commitment to each other will be, what you would do if you had pregnancy complications.
It is, honestly, what mature planned parenting is all about.
You just sound like you did it on a whim. You could be paying for that for a long time.