I had sex for the first time with my boyfriend 7/18/14. my last cycle was 6/25/14-6/29/14. i took plan b one-step right after. could i be pregnant?

It's highly unlikely: It's highly unlikely that you'd be pregnant if you had intercourse 2 days ago and too plan B immediately after, but nothing is 100% guaranteed to prevent pregnancy. One way to help prevent pregnancy & STDs in general is by using a condom. If you have any further concerns, you should discuss this confidentially with your primary physician.

Unlikely: It is unlikely that you are pregnant if you took plan B within 48 hours of sexual intercourse. You should, however, monitor for your next period. If it missed, then consider taking a home pregnancy test. Best wishes.