Sore breasts after plan b?

So my boyfriend and I had sex, but after about a week, I noticed my breasts were feeling tender to the touch. We had used a condom, but after some reading I discovered that tender breasts can be an early sign of pregnancy. So I took plan be to be safe. It's been about four days since I took it, and my breasts are more sore than ever and swollen quite a bit. Including around the nipples. Is this a sign that plan b is not working? I did see breast soreness as a side effect, but nothing about swelling so I'm concerned. The pain seems to be mostly on the outer sides of my breasts. Any advice or insight is appreciated.