sore breasts are caused by changes of hormone levels in the body. Typically when you ovulate, you will find that your breasts are more tender than the rest of the month. The two most likley culprits are caffeine and estrogen dominance.
To decrease estrogen levels in your body do the following: avoid hormone based foods like chicken, meat, fish, dairy. Buy organic or local produce because pesticided have estrogen like effects in the body. Avoid cooking in plastics. And avoid caffeine start. Don't think you need to do all of these, but each one has an impact on estrogen levels. If the soreness continues seek professional help.
Pain in the breasts can be a different story, so I would seek professional advice. Don't play with it.