Hirap yan, mama! At 33 weeks, ligtas lang ang occasional back pain at Braxton-Hicks (yung tigas ng tiyan), pero kung palaging masakit ang balakang at pare-parehong tight ang belly, better check with your OB na lang para ma-rule out kung hindi something else, one of my mum friends had similar symptoms at kailangan lang ng proper positioning at exercises, but you really need to confirm with your doctor. Jangan lang mag-alala, usually normal lang yan toward the end, pero it's always better to be safe at ma-assess ng doctor na talaga.