I am not pregnant and my left breast is increased in size and very sore. It is painful what could this be?

When mine did this it was cystic breast... caffeine makes the problem worse.

What are they ways they treat that is it cancerous or anything?

I just got yearly mamograms and went and had my breast examined every 6 months, sometimes they would aspirate the lumps if it did not go away on its own or when they put the needle in. Really all they told me was to watch out for the caffiene products, that helped mine a lot... for some reason after I had my kids the problem went away. I am 45 now and had the problem since my late teens.