Eh tu normal laa, most of us ada rasa macam tu towards the end, the tightening sensation tu likely Braxton Hicks contractions, esp kalau random je and tidak regular. The back and pelvic pain tu common jugak because baby dah settling lower, putting pressure on those areas, tapi kalau tegang tu makin frequent or discomfort becomes unbearable, better check with your doctor to make sure everything on track. A few of my mum friends juga experience the same thing around 39 weeks and eventually labour came within days, so your body might be preparing even if you're not seeing obvious signs yet!