Aww sayang, that hardening feeling tu most likely Braxton Hicks contractions, totally normal at 33 weeks, ramai dari my mum friends experience the same thing, especially when baby moves around. Tapi since you're already at 33 weeks and it's causing you worry, better check with your doctor or midwife to make sure everything's okay, especially since the pain goes down to your thigh area, they can examine you properly and give you peace of mind. In the meantime, try resting, drink plenty of water, and if the contractions become very frequent or painful, don't wait lah, go to the hospital okay?