<<Seems like if the Medicine was doing that to me then I'd have started the symptoms before then.>>
Not necessarily. People's tolerance for things can disappear. I used to be able to consume some sugar alcohols, but over time my tolerance to them lessened and lessened until now I tell people I'm allergic to them because just a breath strip gave me bad gas cramps hours later. I didn't used to have that reaction.
Also, your medicine can make certain situations worse. You may be okay most of the time, but if you eat beans, man, it's worse than if you had not been on the medicine at all. So changes in diet can affect how your medicine works.