Sarah,
A couple of thoughts..
1. Send us a picture of your equipment pad, showing the filter. Two pics from different angles would be best. We need to be able to tell what size and brand the filter is..
2. If you have not done so yet, it would be best to open the filter and completely clean it out, so that you have a known starting point.
3. Most DE filters have a valve that allows you to backwash them. When you backwash you are never able to get them completely clean, so you only add about 75% to 80% of what you'd put in when completely clean.
4. At the top of the filter should be a pressure gage. You will need to backwash, or clean, whenever this gage gets 25% to 30% above the "clean" pressure. This is why I suggest that you start with a completely clean filter, so that you know what the "clean" pressure is.
Jim R.