Alamak, sakit belakang masa breastfeeding memang payah, a few of my mum friends had the same problem, especially when toddlers pull and tug while feeding! Posture masa nursing dengan anak yang aktif memang challenge, so try to support your back dengan bantal atau cushion bila dia feeding, and kuat-kuat adjust position instead of bending forward, buat sure your shoulders relax sebab tension there jejauh ke belakang. If the pain is really bad or tak hilang, better check with your doctor to make sure everything okay, but honestly stretching and maybe a gentle massage from hubby boleh help juga, I swear!