I know exactly how scary and uncomfortable this pain can feel, especially when it's so constant. It is completely normal as your body prepares for the baby, so please try to take deep breaths.
It is just your body's beautiful way of preparing to nourish your little one. Embrace this change, and remember that this soreness will settle down as your pregnancy progresses.
Your breasts are preparing to feed the baby, so the milk ducts are growing. Just buy a supportive, non-wired cotton bra one size larger, it gives immediate relief without costing much.
Oh god, the breast tenderness in the first trimester was actually insane, yaar! It's just estrogen and progesterone doing their thing, so get a seamless cotton bra and you'll feel much better.