Confused about Diet Changes, BF and Colicy Baby

DS has had severe gas going on since he was born. I cut dairy out 2 weeks ago and he is still gassy so I am trying to eliminate other things from my diet. I know it can take up to 2 weeks for dairy to get out of your system. But I am confused...he was super gassy and fussy yesterday so does that have to do with what I ate the day before yesterday? Or could it be from up to two weeks ago? If it's the latter, how the heck will I ever be able to figure out his trigger foods??? He's been fine today?