Are you clamping over and under - that is, gluing with one clamp under the boards and the other clamp on top of the boards and so on in a staggered pattern? This provides equal pressure across the boards and helps prevent warping and cupping.
One other thing I could think of is ..... is your table saw blade at exactly 90* to the table? Just a hair off could result in a cupping similar to barrel making where all the edges are angled.
Just some thoughts.
As for straightening the top out, I have never had any luck doing that. I go with some of the other guys on slicing the top up and re-gluing. Then flatten out the small ridges with a planer or a belt sander.
Tony B Retired woodworker, among other things.
"Strive for excellence and settle for completion" Tony B