Losing weight but breasts are increasing in cup size, recently I have had a really sore back, always had a large chest but never back problems til now?

Pregnant? . Enlarging breasts after puberty is finished for most women, especially with weight loss, always makes me think of pregnancy. You could be just increasing your breast size later than usual. If you are having pain due to size, i would see a doctor to discuss reduction. But either way be sure you're wearing a very supportive bra that is the correct size.