Thanks for using JustAnswer. No, this does not mean that your teeth are going to fall out. They could be spreading due to some habit. When you swallow, your tongue may be pushing your teeth forward. This would cause your teeth to spread. This is called tongue thrusting. The way to check this is to look in the mirror and see when you swallow if your tongue is coming through your teeth. If this is the case, you will need to try training your tongue to stay on the roof of your mouth while swallowing. The constant pressure will cause you to get spreading of your teeth.
This would be my first choice of what is happening. Another thing would be if you have had to have teeth extracted. If so, your other teeth will start sliding into the space where a tooth is taken out.
Again though, just because you are getting space between your teeth, does not mean that your teeth will fall out.
Hope this helps, I would be glad to respond if needed. Best of Luck! Dr. Cliff