Put it in for 20 seconds , no condom, didn't cum or precum could i still get pregnant?

Maybe: A little semen when the penis is erect in the vagina and the male is sexually excited even for 20 seconds sometimes a tiny bit of semen will seep out full of sperm. Don't take chances. Those sperm are good swimmers.

Not 0%, but: Not likely. Depending on your ovulation cycle and the fertility strength of both of you, it is possible - not as likely as if he'd cum inside fully - or if there was visible pre-cum. Still, there could be a bit of sperm. It is always a good idea to use protection when being sexual. Think of it as self-regard for both of you - it's a good habit to get into and shows each other that you care.