Do some situps without feet support, with a rolled up towel under the small of your back. And do some Russian twists with minimal weight on a decline bench. This has been killing my abs...
I do Needsize's with a plate on my chest, and more seconds per rep every other day along with side crunches. The other days I do 300 sit ups, 10 minute bridge, 3 minute leg lift. Seems to work