Could you be pregnant if you and your boyfriend had unprotected sex a day after your period ended and he pulled out without comming?

Yes. The pull out method is a myth. There is sperm in the fluid that comes out before an orgasm, as early as the first arousal. Also, not all women are the same when it comes to her period. Some have multiple periods in the same month, several days where it stops and begins agian, multiple egg release, etc. Its not safe to assume you won't get pregnant the day after a period.