Why would singulair start working then stop?

I may not be the best person to answer this question because personally did not find Singular helpful at all, but that was just me. I was found to have other problems after extensive testing. I would call your doctor and tell him just what you said in your posting. Also it would not hurt to ask your pharmacist what amount time it takes to get results from Singular. Some drugs take weeks or months before results are seen and the fact that you felt good for the two weeks may not have had anything to do with the drug but it may have had everything to do with it. Time to ask questions of the experts, the doctor and the pharmacist. Sorry I could not be of more assistance to you. Good luck and feel better.