I know how you feel! When I first started breastfeeding it hurt sooo much when my milk came in! Extreme pins and needles as you've described. After a few months though it got better. I don't think anything is wrong. How old is your lo? My son is 6 months now and the painful letdown stopped about two months ago. I wouldn't get too worried about it. I've read about lots of women who experience this as well. If it does get worse and you are really concerned I would as your pediatrician.