Transiting moon in Gemini - Happiness and sadness

Hello. I have been having an odd mindset for awhile. For an hour or so I can be very unhappy with pessimistic thoughts (possibly because of my uncontrollable imagination triggered by the state of my mood, as I have a very strong Neptune in opposition aspect to my Mercury) followed by a very high amount of happiness with optimistic ideas. Frankly, I have gone through a pretty hard depression, had psychological problems and have been taking proffessional help. Is this situation harmlessly caused by transiting moon in Gemini or is there a more serious problem such as bipolar disorder?

In addition, I can not sleep when I want because I can't stop thinking. This has turned me nocturnal lately.

Here is my chart.