I took an plan b and got on birth control at one of my doctors visit. 4 days later my boyfriend ejaculated in me. could i be pregnant?

Probably not: Hopefully, the Plan B or the birth control pills are working, but it may be too soon to tell about pregnancy. A urine pregnancy test, done correctly, gives a reliable result 3 weeks after sex (3 weeks after when conception might have occurred), or 1 week after missing a withdrawal period. If done sooner, a positive result is likely real, but a negative result may be due to testing too soon.