Hi & Welcome. Yes, feeling sick or tired, tender breasts, nausea, headaches, lower abdominal pain are the common side effects that occur after taking Plan-B. These are not the typical signs of pregnancy and the fact that the pregnancy test is found be negative, the chances of pregnancy are almost negligible. These symptoms usually subside within a few days. If the symptoms do not go away or get worse you must consult a doctor. Most females will have a normal period at the expected time, but some may have their period later or earlier than normal. You might also have some irregular bleeding until your next period. If your period is more than 5 days late or is unusually light or unusually heavy, or especially painful, you should consult your doctor. Hope this answers your query.