Ok I checked my floor and the following is taking place, also a description of the room.

The room is 15'6" by 15' 6" and from center of room out 5' it is flat with about a 1/8" to 3/16" out of level. the outside 3' the floor dips down almost 1 3/4" down from the top of floor center. how or what do I put down on sub floor to get floor flat? I have heard of using shingles but what is the best or most economical way to flatten it?

Bryan

PS how do I add a photo so you can see the sub floor?

I doubt you can fix 3" with shingles. Sounds like a structural problem. Hire an expert.

Ya, a floor that out of whack is gonna require some structural changes.
I dont think the average DIY'er would find it a project to take on.
Most likely, a GC will be needed to remove the subfloor down to the joists and flatten from there, then re-install the subfloor.