my girlfriends breasts are very sore and swollen. wtf?

[Turtle Head]

her breasts are swollen to the point that they are noticably much bigger. they are also very sore, to the point where she has just been hanging around the house with no bra on because wearing a bra is extremely painful right now.

her period is not due til the 15th. i bought a pregnancy test and it says she isn't pregnant. the odds of her being pregnant are really small anyway since we hadn't had sex for around a month and a half until 7 days ago, and we've worn a condom the few times we've done it since then.

are there any reasons her breasts might be swollen up? am i correct that a pregnancy sign like swollen breasts wouldn't show up this early if she was pregnant somehow? and if they did show up early they would not happen at least until after the first time she missed her period?

cue 100 "she's banging other dudes" responses.