Sudden depression "relapse"?

Looooong time no see forums!
Last time I posted here I was 19 and now I'm 21. A lot of stuff have gone down, and most of it has actually been pretty good. I'm back in school (I've managed 1½ years with "only" 3-4 days off every month ^^), I like my class, I have some fairly good grades and know how to handle myself and my anxieties, and doing this drug-free.

The reason why I'm posting now is in the title:
Everything is going so well, but lately I've felt much sadder and tired than usual. It feels like someone has taken the feelings I had 3 years ago and thrown them at me, completely unexpected!
I don't know what to do! I've been doing so well, and there's no reason for me to feel horrible again? I'm so afraid that this is just the start of something much worse, and I can't do that - I want to finish my degree that I've worked so hard to just get going on, and keep my new friends.
I'm just so scared that all the bad things will happen all over again and kick me back to square one...
And if you want to tell me "slow down": I literally can't slow more down without starting to go backwards... I'm already doing as "little" as I can, with as few stressfactors as possible.

Have any of you experienced something like it, or have any advice?

PS: I'd like to apologize for some of my ridiculous ramblings on here, those years ago: I was a frustrated and pathetic teen who just wanted some attention

The idea of relapsing scares the hell out of me. But apparently it's happening to me, too, anyways.

Everything is going so well, but lately I've felt much sadder and tired than usual. It feels like someone has taken the feelings I had 3 years ago and thrown them at me, completely unexpected!

This is almost exactly how I've been feeling, and I'm sorry you feel like that too. Obviously I don't have any advice, but I could talk about it if you're interested. I hope you make it through this!

I think relapse is really common, at least it is for me. I started having depression episodes when I was 12, and then it seemed like I would recover, but then a few months later I would feel depressed again. It's been a cycle like that for me ever since.

Have you taken medications for it? I see a therapist now and she seems to think I need to be on medications because my mood is always down even for no reason.

Thanks for the replies guys

I have tried different meds, but none of them worked for me - they simply didn't have an effect - except the side-effects!
But do any of you think it would be a good idea to see a therapist? I just don't want them to tell me that I can't handle school, or something like that :/

If you explain that you're handling school pretty well, then I don't see why they'd tell you to slow down on it.
I feel like if you want to see a therapist, it's best to go with specific issues in mind that you want to vent about/work on. That way you'll be less likely to get weird suggestions like slowing down on school. If you have something specific that triggered a relapse of depression this time (it happens to me), then you could bring that to them.

Also, see if your school offers free counseling/therapy, so you can try it and see how it goes. That's how I get therapy, I try to keep my parents as uninvolved with the process as possible.