Why the sadness?

I just had an unexplainable wave of sadness hit me a little under half an hour ago...don't know where it came from. I was feeling fine one moment, and then suddenly, boom...sadness. I don't know what to make of it. Also, it's not going away, so looks like I'm gonna be stuck with it for a while. Now I don't know what to do about it. Not sure if it's depression coming back to swallow me or what...Should I be worried? I'm familiar with depressed moods like this, but what I'm not used to is having one take over me so...suddenly. I also currently don't have anyone IRL to talk about it with, so I'm relying on you guys...

What should I do? I suddenly feel like crying and everything seems bleak and hopeless...

Are you taking any medication? What is your history with depression?

I'm not currently taking meds & am not seeing a therapist. I can't at the moment.
And I've had depression for going on about five years now.

This kind of sadness can mean that you are healing. You will feel it as you let go of familiar bad feelings such as consent depression, and the like. It is like saying good bye to an old friend.