Left leg pain

I’m 26 weeks pregnant with my second child.

For the last couple months my left leg gives up on me , im always standing, walking at work and at home and out no where my left leg gives up on me I get a sharp pain in the back of my leg and I need to catch myself otherwise I will fall. Has anyone experienced this ? I mention to my dr and she said it might be the position the baby is at. The pain is very bad I feel like one day I will fall and hurt myself and my baby . Any ones has experience this pain? What should I do ?