If you have been taking your birth control amazingly, no antibiotics, no missed days or freakishly late timing- you're highly covered (98% usually). Added to that fact he didn't fully ejaculate, and the effectiveness of the plan b- I'm going to say you can sleep easy. That is a very very small chance you got pregnant.
Keep in mind the plan b is likely to have some side effects. These include nausea, headaches, back pain, bloating, cramps, fatigue, etc.