Bitcoin transactions slow to confirm for past month

I've noticed recently, for the past month or two, that Bitcoin transactions have been incredibly slow to confirm. Often taking hours, sometimes taking days to confirm. It isn't for one particular site, but for every site online. I've paid using BTC on multiple sites.

Does anyone know what is going on? Why are confirmations so slow now? Did a large mining operating stop mining which resulted in slow transactions?

EDIT: For anyone interested, I found more information about it in this article. It is due to a backlog in the mempool (memory pool).