Speed or Sanity?

I started taking Singulair for my asthma (exercise-induced due to allergies) about 3 weeks ago. I noticed a great change in my breathing ability, and I was able to knock down my pace by at least 30 seconds per mile, which felt amazing. I was also able to run some miles under 8 minutes, which I have really been struggling to do. But then I noticed some strange things going on. First of all, I gained about 4 pounds in three weeks, even though my mileage was around 30 per week, and steadily increasing. I was also feeling some depression-like feelings coming on, even though things are all really good in my life right now. Finally I figured out it was probably the new drug. I went off of it two days ago and have already lost 2 of the 4 pounds. I also feel very happy and not depressed at all. Thank goodness for that! Now the bad part, I went for a 7 mile run today and could hardly get my pace faster than 9:30/mile. I did 14 last Saturday at 9:20 and it felt so easy. Obviously the side effects are not worth taking the Singulair, and I'm going to ask my doctor for another option. But in the meantime, I'm wondering if anyone out there has had success with some other asthma medications. I'm running a marathon on May 30th and then doing the Wasatch Back relay in June, so I need to be healthy and able to train for several more months. Let me know if you have any good information!

Amy