Oo, normal yan sa 36 weeks, sis! Ang baby is getting bigger na kaya mas maraming pressure sa lower back, hips, at pelvic area, marami sa amin na dumaan dyan at sobrang uncomfortable talaga. Try sleeping on your left side with a pillow between your knees, or use a pregnancy pillow kung kaya mo, isang kaibigan ko swears na yun nag-save sa kanya ng sleep quality sa last weeks. But since may matress pain ka rin and it's causing you discomfort, siguro best to mention it sa OB mo next check-up para ma-assess niya properly, just to be safe. Hang in there, mama, kaunti na lang!