Took plan b right after unprotected sex. on birth control regurarly. is there a chance to be pregnant? had protected sex the next morning.

Yes: There is always a chance to become pregnant with every episode of unprotected sex. Plan B is approximately 75% successful at preventing pregnancy, but you won't know the answer until you wait to see if you miss your period. Also, Plan B can cause some irregular bleeding that you might not be certain whether it is/is not your period, so I recommend taking a pregnancy test in 2-3 weeks to be sure.