It sounds like you’re currently very depressed, do you still experience the elevated moods (mania) associated with Bipolar Disorder? Please go back and talk to your GP, meds can have positive results for Bipolar Disorder. I know it’s difficult to even get to the GP a lot of the time, but please try. Biking has obviously made you happy in the past, you need to remember how great it can make you feel. Force yourself out on a little ride, or something else that was fun for you in the past, and use the elevation in mood to get to the GP.
CBT (Cognitive Behavioral Therapy) will help you to recognise your mood/thought/behaviour patterns and triggers, and give you more control.
If you’d like to talk privately, my email is in my profile