Handling Overwhelming emotions

I am doing good for the past 2 days.
But I don't know if it is due to bad humid weather, I am feeling very low today.
My core problem is, which many of my loved ones have said that I back and forth between hyperactive and dull phases.
I easily get high on emotions and I cannot handle my feelings and thoughts when I am in hyperactive phase which I was today. And now I am in a dull phase. I developed a habit nowadays of going to the gym but due to the dull phase now I came back home after 30 minutes of cardio. Don't know how to come out of the dull phase.
I guess it is bipolar disorder. I think that is reason I watch porn,(in my dull phase).
Any suggestions are welcome.