No problems about being clear -- it's hard to be clear about something, when you are not experienced with it!

From what you describe, it definitely sounds like you've got a typical sand leak, that puts sand into the pool under the returns. Best way to check, is to vacuum it up so none is left, and then backwash again and see what happens.

If the filter IS leaking sand, the easy fix (depending on the filter) is to open the filter, examine the air bypass assembly, and correct any problems with that. The harder fix is required when the leak is in the "laterals" or "header" at the bottom of the filter. To fix that, you have to remove all the sand, and then replace the parts with cracks or damage . . . being very careful to not crack any of the others.

Sending some pictures of the piping and filter would DEFINITELY help us, help you. Send them to poolforum@gmail.com. Try to get some clear pictures of the filter as a whole, and also of the manufacturer's label on the filter. Don't worry about sending pictures that are too big -- I can shrink them, but if they're too small, I can't really make them bigger.