Oo, totally normal yan sa stage mo na! Most of us sa third trimester nag-experience ng cramping at lower back pain dahil sa weight at how baby's sitting, lalo na kung active ka ng walking, yun talaga ang common culprit. The on-and-off nature mo (pasulpot2 lang) is actually a good sign that it's ligament stretching and not anything serious, kaya kung tolerable pa lang and no bleeding or super intense contractions, mas okay ka pa. That said, since you're almost at 34 weeks, best to mention it sa OB mo sa next check-up just to be safe, especially pag may sudden changes, pero honestly, I think you're fine given kung paano mo describe it!