Sore breasts.

So, recently I noticed that my boobs have been sore more often than not, and that they're bigger than they were just a couple months ago. My boyfriend and I noticed it and we both agreed theyre bigger than they were when we first started dating. It's not like a drastic change, but apparently it's noticeable. My breasts had been the same size since I was 15, I'm 20 now, and I'm curious to know if it's normal for them to get bigger even in my 20s. I'm only an A cup, so they're not like huge haha