29 yo female, history of anxiety - well controlled under normal circumstances.

I stress ~extremely~ well-controlled under normal circumstances with just cognitive behavioral therapy, no medication. Meaning I feel perfectly normal around 85-90% of the time.

After a bout of flu and a lingering cough, my doctor prescribed Singulair. Five days later I was having panic attacks, nightmares, and depressive thoughts - all of which are very rare occurrences for me unless something ~majorly~ stressful is going on. Yes- just five days on the Singulair.

I felt very much better a few days after stopping the Singulair - but not completely. It's been a little over a week and I am still experiencing higher than my normal incidences of anxiety, nightmares, depressive thoughts. The intensity has lessened quite a bit from the completely out-of-control feeling on the drug, but I am far from feeling normal.

Is this a common occurrence for those with adverse reactions? How long does it take for the average adult with a strong adverse reaction to the drug to re-normalize?

Other medications taken at the time -
Mucinex DM as needed
Albuterol as needed
Methimazole 2.5mg 2x a day - Graves Disease but ~NORMAL~ thyroid function at this point in time

Other considerations:
Currently pre-menstrual, which does tend to increase my stress a little bit but not to the current, post-Singulair degree.

Thank you in advance.