Ay anak, 12 days pa lang kaya totally normal yan, parang may slight engorgement or buildup ng milk pa talaga sa first few weeks, lalo na kung recently ka pa lang nag-start ng breastfeeding! A few of us moms experienced the same thing kaya don't worry, but since baby mo is still so young, it's really best to check with your pedia or midwife just to make sure everything is okay and walang mastitis or anything like that.