Aih, congratulations on your first pregnancy! Ligament stretching is super normal at 19 weeks, ramai mums in my circle went through the same thing, rasa macam pulled muscle betul2. Tapi since you're saying it's quite painful and affecting your movement, better check with your doctor just to make sure everything's okay, especially first time. In the meantime, try move slowly, take warm baths, and rest as much as you can, the tightness should ease but don't push yourself lah. Ini very common tapi best la confirm with your gynae untuk peace of mind ye!