My boyfriend and i had unprotected sex , immediately i took the plan b. the next we had sex , he did not came inside me but instead on top me. can u get pregnant this way ? or does the sperm have to enter via penetration for this to happen.

Risky: If he was inside you at any time without a condom you can still get pregnant even if he didn't ejaculate inside. A small amount of sperm can leak out before ejaculation. Always use contraception!

Precum with sperm: Sperm have to enter vagina for pregnancy to occur. However, pre-cum, which neither U or partner may feel, in vagina can result in pregnancy. Hence need for condom before vaginal penetration. U can check by pregnancy test a week after due date of next menstruation if u don't have a period. Suggest bf use a condom from the start as it is best way to reduce fear of pregnancy.