I am pretty worried. My girlfriend took plan b step one and only 2-3 days later she told me her breasts have become sore. I have heard this is a side effect from plan b but how early can this occur? I have read that other people had the same issue but it happened in 2 weeks not a few days. Can somebody help? Has this happened to anybody? And also. Her period is supposed to start in the next 3-4 days. Could this also just be a sign that she is about to start her period? She told me its the first time it has happened in a long time but i have also read that sore breasts can also just mean you are about to start your period. Please help!