Oo, normal yan sa third trimester, lalo na ngayon na 36 weeks ka na! A few of my mum friends experienced the same thing, parang may space na doon kasi lumalaki na ang baby at umaangat ang uterus, so nakakasakit talaga ang side. The ligaments are stretching din, kaya that hollow feeling is common, pero since this is pregnancy pain, mas safe na i-check lang with your OB just to be sure lahat is okay with baby and positioning.