I didn't take a plan after the first encounter but 4 days later i had another encounter and took a plan b pill in the 12 hour period is it possible to be pregnant from the first encounter?

Plan B, is emergency contraception you take within 72 hours after unprotected sex. It contains a high level of hormones that blocks ovulation and interferes with the implantation of a fertilized embryo and resets your menstrual cycle. It is not effective after 72 hours so you could very well be pregnant. Take a home pregnancy test which can be positive as soon as the first day of a missed period.