Thanks for your query
Yes gastric irritation occurs in case of motelukast after prolonged use and probably that is causing your stomach pain and digestion problem and sleepiness probably is occuring from levocetrizine component of the montek-LC medicine. So if your symptoms are well controlled now you can omit this drug now.
Better to go for local application of azelastine fluticasone nasal spray
now after consulting your doctor. For stomach pain you need to take local anesthetic
gel like mucaine gel for symptomatic releive and pantoprazole
tablets for healing of the erosions if any by montek-lc.