If dirt shoots back into the pool when you vacuum, you have a problem.

1) Your pump may be too big for the filter, and is forcing the dirt through the sand.
2) Your pump may be too big for the filter, and has blown sand out during backwashes,
so now you don't have enough in the filter.
3) Your filter may have some other problem.

Fix #1 by putting a valve between the pump and the filter, and closing it partially OR by having a service guy replace the pump's impeller and diffuser with the next size smaller (not possible on all pumps) OR by buying a new smaller pump OR by buying a bigger filter.

Fix #2 by opening the filter and adding filter sand. Then, since your pump is STILL too big, consider your options in #1
above.

Fix #3 by repairing (?? whatever it takes -- I dunno what all it might need.) your filter.

Just to be sure, you can do the "DE filter test" on the filter. (There are a few types of dirt sand filters won't catch -- even when they work properly.) Add a small amount of DE ( 2 cups should be plenty) to your skimmer while the pump is on. Watch your pool returns for 5 minutes. If the DE shoot back out into the pool, you have filter problems.

Oh yeah: DEFINITELY run the pump 24/7 till you are ALL cleaned up.

Ben