Could it be IBS or diet?

So my dad has either ibs or crohns disease, the doctors were leaning more to ibs and said they could make a proper diagnosis in london but my dad refused this. Lately I have found that I go to the toilet normally and stuff but occasionally every month or so I get a very slightly upset stomach (only slightly). For example this week I went 3 times in 24 hours and Im going normally now but my stomach feels upset and at night I can get stomach aches and nausea and it makes very loud noises (basically like gas, this happens every night but is normally not accompanied with pain until last night). I was kind of thinking though, for this to be ibs, wouldn't I have to have these symptoms every day continuously and be going to the toilet alot? Could it be something Im eating that my stomach doesn't like or perhaps not enough solid foods or something?