It suggests Bipolar II (I am not sure they use the division between I and II in UK, though, but basically bipolar with depression and hypomania, but without frank mania). You also a very eloquent person .

This site has a Mood tracker: Mood Tracker - Track your daily mood on Psych Central

I would track moods for three months and then take the mood tracker to a psychiatrist (not a therapist). It is also surprising the current therapist has not picked up on your phases, since they seem so textbook.

As an alternative to this side's Mood Tracker (or an addition to it), you can use Optimism Online, which is customizable, and in your particular case it would make sense to track when you start what is called "self-medicating" with alcohol, to see if you can unearth patterns of correlations between phases of mood and drinking.

In general what is happening with you is called mood congruent memory, which is a type of cognitive bias that makes you recall events of the same affective (mood) state as your current state. For this reason you are getting flashbacks of past negative or shameful situations when you are feeling very low. Also for this reason you think that the productive stage was an illusion - it feels so because it is hard to recall (to feel that it was real) a state that is starkly different from your current state. This bias is a trick the mind plays on us.