light source is too far away. You have a light over it right? Its stretching because its trying to reach the light it requires to grow the leaves your missing. There are two things you can do at this point to keep it from falling over and dying:
1. transplant it into a slightly larger/deeper pot and bury it until just the top inch or two is sticking out of the soil, give it a spray and put a light over it OR
2. stick a pipecleaner, bamboo stick or something next to the plant and loosely tie it for support. Make sure a fan is blowing just enough air on it to make the stem wobble in the breeze. It should be strong enough to stand on its own in a week or two