My breast have been sore for the last couple of days. I thought they'd be sore for a little while, but as the days go on, they remain sore and more sensitive than before. I don't think my breast are growing, they haven't changed, but I don't really know because they feel heavier than before. I checked for abnormal lumps and any strange things, but I've come up empty. They've just been sore and sensitive for a while and I don't know what's going on. Is it a puberty related thing, as I'm still 18, and if so, what is it?