I'm not sure if corn would be a problem for you, but if you tried GF and had lots of corn products, try next time not having lots of corn products.
I eat both white potatoes and sweet. I have quinoa flakes and quinoa grain. The grain I use as a substitute for rice sometimes with stir fry. I've only had buckwheat noodles, haven't tried the groats because I haven't found them yet. Amaranth I get in the form of pasta (amaranth flour + rice flour), flour which I've made tortillas with (they didn't turn out great but work ok), and puffed which I mix with unsweetened almond milk and berries, or peanut butter. I eat rice most days, but usually only about 1/2 cup or so per day. Don't cut rice out, but try to incorporate other foods so you aren't eating too much rice.
I've had IBS as long as I can remember. I can't remember a time when I didn't have stomach pain and difficulty digesting. Now I finally feel great, and so I would say I'm not angry I have to eat this way. I never knew I had it so bad my whole life and at the same time never knew what it was like to be normal. I don't feel restricted on my diet, I love vegetables, fruit, fish, nuts etc... I love the fact that now I don't have to worry about what I'm eating and when and how much fat there's in it. Although I follow Heather's diet in terms of avoiding the triggers, I'm not really following the fat content rules or SF first.
As for sweets and dairy, I used to live on that stuff. Now that I've changed my diet completely and pretty much have no added sugar, I'm enjoying the actual "true" taste of foods and it's wonderful. I love the taste of strawberries just on their own, whereas before I used to coat them in sugar. Sweet potato tastes great without adding butter to it.
I would say I've come to find new foods that I love. Kinda like getting over an old BF, I don't really care for the dairy or sweets anymore. I love my new foods and I'm committed to them!