Fall seasons symptoms and conditions

My husband has been taking Singulair for the last two years. It has made a tremendous difference in his frequency of sinusitis in the winter and allergy symptoms during the summer and fall seasons. For at least the last year, he's been having trouble with insomnia, so he is taking Melatonin. This helps but last night something very new happened. We went to bed around 11:15 p.m., then at 12:45 he woke me up and said he was having trouble breathing. He was very agitated and paced around the room, would sit for a few minutes, then get up again, pace and act very agitated. We've been married for 26 years and this is not normal. We almost went to the emergency room but decided to wait. This morning he's tired and very quiet. From reading the other postings, I think that Singulair could be causing the insomnia and now the agitation and depression.