8 weeks pregnant and my breasts have gone up a full cup size and very tender what is the best to sooth them i was told cucumber?

Cold!: Well since you are right in the stage of development when fetuses are most vulnerable to teratogens you have few options. Thankfully ice bags or cold compresses are one if the best and most appropriate methods to decrease swelling naturally. Try applying cold 15 minutes every hour and increase duration as necessary. Wear a really supportive bra 24/7.

Breast pain: You should wear a tight bra, better to use a sports bra without an underwire. Also keep ice packs on them when you are able to. Avoid them being stimulated more than necessary and it should get much better after 12-13 weeks. Good luck!