No, it's not at all TMI... not if we can talk about how frequently our lower intestine is active, on this forum. ^-^
Mine did this too. I actually hit my TOM a full week early (during P2), still lost during it, but my breasts got REALLY tender and swollen. It eventually went away -- I was retaining water like a fiend, but once TOM left, it was all good. :)
I remember when I had my first son and within a week or so after having him I was getting in the shower and noticed HOT DAM my boobs were like double in size i was soo excited that i actually was screaming for my husband to come look he thought something was wrong and i was like look at my boobies omg i love them "take a pic" hehe he just chuckled at me .. well it was short lived very short lived...as of right now they better be sore from TOM coming on or I will be forced to choke hubby