What Causes Pricking Sensation In Breasts During Lactation?

Im having a pins and needles feeling in both breasts after I pump milk. I have twins that I produce milk for and they are now 4 months old. I have had cystitis after this delivery and was treated with antibiotics. Previously , I have had mastitis twice. It hurts throughout the day, do you have any suggestions why this is happening and what to do for it, thank you