How long did you try to follow the low carb/high protein/high fat diets for? I was from the same high carb school. I ate oatmeal for breakfast, bread at lunch, pasta at dinner, and just ate all the potatoes, sandwiches, spaghetti I could. I come from an Italian family, there's always bread and pasta in huge quantities. My protein was usually one egg with breakfast, whatever lunch meat I picked, and maybe a little ground beef or chicken at dinner. And I ate like this from my childhood all the way till I was 23. Then I found Robb Wolf.
I started playing with things, not paleo, but just eating more meat. Then I started eating more fats. I wasn't low carb by any measure, I still had oatmeal for breakfast everyday, and my post workout shake was milk with berries and a scoop of protein (not a terrible choice, but not what I do now). I had been doing Gym Jones, and then switched to Crossfit, at which point, I started zoning still eating grains. My performance flatlined, I stopped progressing, and I contacted Robb directly, and then everything changed.
I went wholesale paleo. I felt awful! My workouts sucked, my runs sucked, my swims were slow and hard. I stuck with it though because I thought, if this works for everyone else, I'm going to make it work for me. After about a month, suddenly, it was like someone flipped a switch. I had more energy, I was sleeping better, I was less sore after workouts, I leaned out, suddenly I had abs, my acne cleared up, and I stopped getting "the runs" after long runs. Now, I feel and perform better eating paleo than I ever did eating high carb.
Could your body have adapted to your high carb diet? Definitely. And that's probably why you do so well on it. Look at Michael Phelps. The guy eats carbs like Lindsay Lohan snorts crack. But, adaptation is a powerful thing, so I think if you can stick with it even when you feel crappy from not eating carbs, your body will adapt. I like the saying Food is a Drug. So, coming off a high carb diet, you may feel some "withdrawal." I would try going on full on paleo, if you want an easy guide marksdailyapple.com is having a "Primal Challenge" month, and he has a ton of articles up right now to help people get on track. Increasing your fat intake as Derek suggested will definitely send you in the right direction. But I think you'll find as you replace grains with vegetables, you're going to stop having that insulin fluctuation and start feeling better throughout the day.