Eish, 28 weeks dah rasa penat macam tu memang normal lah sis, especially first baby, pinggang sakit tu common gila because the weight. A few of us tried sleeping with a pregnancy pillow (those U-shaped ones) under the belly and between the knees, and it helps tengok-tengok; some of my mum friends swear by adjusting position lagi, try sleeping on your left side, it's supposed to be better for baby and your back. Jangan paksa jalan lama-lama, better short walks frequently and lots of rest, and make sure you're getting enough support from your partner or family to rest properly lah.