Help, nipples peeling

Am 24 weeks pregnant, my breasts ain't dripping yet but I find that my nipples are losing top layer of skin each day and some kind of like white heads coming out of the nipple base. Also around the hole at the tip of my nipples, there is so much white stuff collecting which I keep removing each day. Then general the whole breast has gotten a darker pigment than the rest of my chest. My breasts ain't sore, not itchy, and haven't grown.

What is the cause and how can I prevent the peeling. Is the colour change normal?

Thanks for the tips.