Stop doing crunches, stop doing planks with your hips almost touching the floor, knees bent, and hips twisted, Stop doing 1000s of sit ups.
These aren’t working your core – Let’s from the very basic core exercise everyone takes for granted – Breathing! If you lay on the floor and you can't hold you abs as if is you where to take a punch and breathe by letting your rib cages expand then you don’t have a very good core, likewise if you can’t brace your abs whilst laying on your back with your knees bent up and sliding your foot out straight along the floor you don’t have a strong core.
You will have to relearn how-to breathe using all your together, this will make a huge difference to your training.
When training your abs and core it important to understand what you are doing and the means of abs and core – abs are just the 6 pack part you can see, your core is every muscle that your lower trunk uses, oblique muscles, abdominals, lower back muscles, everything!
It’s important to have a strong core that stays strong in all ranges of movement and positions, to achieve this you need train your core dynamically, things like Plank (done correctly are incredible) you can add sliders under your hands and whilst holding your core move your hands around the floor, put them under foot and again try and hold that strong core position whilst moving around.
Exercises like Aleknas, Pallof press’, Planks, Bear crawls, Med ball throws(taught correctly), Zercher carries - will work your core really well, efficiently and effectively, you are moving through different plans of movement, using you core in different ways and means the resistance comes from different angles and put the emphasis, which challenges your core stability, mobility and strength. Using your core in in this way creates a great strong core that will be strong enough to take a Mike Tyson punch from any angles.
Please start training your core with functionality and trying to get your whole core bulletproof rather than just a good set of abs.