Struggling

I am really starting to struggle with depression again. The bad times have just started to roll and as much as I try to stay positive, I can't. I try working out to keep my endorphin's up, but the second I stop my mind goes back.
I can't keep my head from going to dark places. No matter what I try. I just want to stay in bed all day. I can't focus on anything. 
I'm just so damn tired. I don't want to go though all of this again, but looking back, I don't think I ever really came out of it the last time.