Ay, common yan sa pregnancy, lalo na around third month when bumabagal na ang movements mo! A few of us moms experienced the same, ung sore back talaga grabe, especially pag matagal standing or sitting. Best thing is to try pelvic support belt or prenatal pillow, pero promise promise check with your OB about it para makasiguro na normal lang at walang ibang cause, kasi baka kailangan lang ng proper positioning or exercises na safe sa baby.