A tack bra. What a wonderful Christmas gift!
With all the Christmas food, you will need som exercise.
Get the tack bra on. Lie on the floor, belly down and hands on the back of your head and the tip of feet under some furniture to assist. Elbows should not touch the floor.
Now lift your head up from the floor at least 10 cm up, bending in you back. And down again.
Do this at least 25 times. Its quite healthy for you back and good for back pains as well. But I'll guess it will not be so good for breast pains for you
You'll need to do this exercise at least twice every day until end of January, but feel free to continue - exercise habits are always good to have.