Sore breast

Samantha • My husband and I are proud parents of two beautiful children, our daughter is 5 and our son is 3 now we are expecting twins due October 11th!
I have a question yall, according to this app the peek of my fertility is supposed to be today. So last night my husband and I had sex but I noticed while we were having sex my breast were sensitive, and today it's worse. The only time I ever experienced sensitive breast was when I was pregnant with my other two kids. What could be causing this?