I have been on Singulair for almost a month (my doctor said it might take that long to see results) but I have had severe diarrhea, nausea, and stomach cramping all weekend. I didn't take my usual dose yesterday due to not being able to keep much down, and I started to feel better. I took my usual dose before bed tonight and now I am up sick to my stomach again. Is it possible that these side effects are just now showing up? (I have a history of GI issues and stomach irritation from other meds)