I have been on Singulair for about 2-3 years during which time I ...

I would look into the possibility that someting other than the Singulair is causing your hair loss. I have many environmental and food allergies (and have been taking Singulair for about 3 years) and have recently been diagnosed with a thyroid problem due to an auto-immune disorder caused by my sensitivities. Thyroid problems are a HUGE cause of hair loss. Other symptoms can be reviewed online with a simple search. Ask your Dr. to run some thyroid tests but DON'T let him or her stop at a TSH (thyroid stimulating hormone) test. It is not a good predictor of early-stage thyroid problems. My TSH was normal and further tests (which I had to really push for) revealed my problem. Ask for a T3 and T4 test and more if they will do it. Hope you find a cause and a treatment soon. Best of luck.