I'm so sorry you are finding yourself in a situation where you are unexpectedly pregnant. I can only imagine how stressful this must be for you.
Unfortunately, you can easily get pregnant if you have sex and don't use a form of family planning, even if neither one of you remembers your man ejaculating.
Even if your partner didn't come, there will still be pre-ejaculate in most cases. Pre-ejaculate is a fluid that comes out of the penis before a man has an orgasm. The fluid can have some sperm in it. And especially if the man recently ejaculated (for instance through sex, masturbation, or a 'wet dream'), the sperm cells can still be active and cause pregnancy.
This is one of the many reasons why the so-called 'withdrawal method' (the man pulling out his penis before having an orgasm, and hence pouring semen elsewhere) isn't very reliable.
Another reason is that it can be very difficult to determine when the ejaculation is happening. This is especially true for young and inexperienced men.
This is why it's best to always use a family planning method when having sex. Condoms are great, because they also protect from many STDs. But if you are faithful to each other, methods like the pill or an IUD work great, and are often cheaper than condoms in the long run.
However, this doesn't help you right now. You are already pregnant, and I assume this wasn't planned. If you are less than 12 weeks pregnant and absolutely sure you do not want the child, you could consider an abortion. But that's not an easy decision, and you should be completely sure this is what you want before making the choice.
The other option is to keep your baby and bring it up yourself. Or with the help of family or friends.
I hope your partner will support you and that your family stands behind you. This will make things a lot easier.
The best of luck to you.
Do you have questions about birth control? Head to our discussion board.