a little DE in sand filter?

[Pokey1]

I have an above ground Intex Ultra Frame pool apx 14000 gal. We bought it 3 years ago. first year was great. Last year I couldn't get it clean enough to swim so I gave up. Not giving up this year. So far its almost perfect. My question is and I've probably been reading too much can you put a little DE in a sand filter? I still have little things in the pool that come up from the floor when disturbed. I vacuum and vacuum everyday and cant seem to get it all. I've backwashed so much I had to get more water! Please no stupid comments I'm trying my best. I really appreciate any help.