We'd like to help. Could you check if you've selected "Notify subscribers" under advanced settings? Also, your subs can check notification settings: https://goo.gl/giVA8o . Keep us posted.
Fluctuation in your subscribers count is normal. We regularly remove spam subscribers or it's probably viewers unsubscribing and subscribing to your channel normally. Here's more info: https://goo.gl/croiE1 . Hope this helps clarify!