No one can tell you for sure what this is just based on your descriptions. Even doctors often get these things wrong. You will probably have to figure this out yourself. I am also wondering if I may actually have SIBO, even though I initially got diagnosed with Candida. I have been treated for Candida for over a year now and have been gradually getting worse and worse. Often SIBO related digestive problems get misdiagnosed as IBS or as Candida.
I’ll share my experience and my conclusions if it is of any help: I get what I thought were Candida reactions to a lot of allowed foods while I could easily have sugar and be just fine. It seems to me then that whatever is easily broken down and quickly digested works for me. The problems arise with stuff like fiber that takes longer to break down and that then apparently feeds the bacteria in the small intestine (my guess). Or worse, due to my slowed down transit time, just sits in the gut and ferments. That is why I am now approaching the problem by trying to deal with the constipation and increase the transit time. That means no more fiber actually as that only made things worse. Lots of olive oil, self-fermented sour cream and vegetable juices work for me. I am also addressing the possible lack of digestive entzymes and hydrocloric acid that might be one problem in not digesting foods properly; I do this by taking bitters before eating, or hydrocloric acid tablets with meals. And I am slightly better, though still very bloated.
Maybe you should just test things for yourself, keep a food diary and note down how you react to foods. figure out the problem that way. Just remember that if you are very constipated and the transit time is slow the food reactions may come a lot later, maybe not before the next day. That is why it is good to test one food item at a time.