You can get pregnant if sperm enters your vagina. This could happen if a guy came on your pubic region or in your anus (sperm could drip back into your vagina), if a finger with sperm on it got inside you, etc.
Best to keep all semen away from your vagina - and to keep in mind that if it's going near your mouth, you'll want to have your boyfriend wear a condom and/or be tested for STDs.