I used to get breast swellling and tenderness anywhere from 2 weeks to 2 days before my cycle. Some months they would be so painful that I couldn't even sleep on my stomach!
One thing that I found, and I know you may say "that is strange!" but, my gyno is the one who told me this and, take it from someone who did it and it is SO true!:
If you drink alot of caffeine products, reduce them and chocolate too (which has alot of caffeine). After a couple of months you will find that the breast tenderness and swelling is reduced significantly!
I have been on Progeseterone therapy now for three months and I have noticed that the past two months I have had NO breast swelling or tenderness! I am assuming it is from the Progseterone although, the first month they were up and down like a helium balloon! Again though, I am assuming my body had to adjust to it.
Well, that is my two cents for what it is worth!!