Bangle 2 battery only lasting 1 or 2 days

Well, the fallback is to just Install Default Apps to reset your Bangle and see if that helps... But:

• Does the Bluetooth icon keep changing color? If so it'll be some device that keeps on connecting/disconnecting as you suggest
  
• What are you Settings->System->LCD settings set to? Maybe turn Wake on... off for everything apart from the button
  
• You could ensure your LCD timeout in that same menu is set low
  
• What apps/widgets do you have installed? Things like sleep tracker will drain your battery fast at the moment.
  
  

Other things that can run the battery down quick are if you have the 'recorder' app left on (which turns GPS on) or if the heart rate monitor is set to on in 'health' settings. Setting the health app to 10 mins gives you a good balance of battery life and accuracy

Updating to 2v12 firmware will probably help you too.