Relapse PPD...???

Is there such a thing as relapse postpartum depression?  Ugh! Yesterday, from the time I woke up until the time I went to bed, not sleep mind you cause that wasn't happening, but bed, I was really depressed ALL day.  And does it matter if I'm trying to figure out if it's a relapse of PPD or is it regular depression, or whatever?  And I hate how my mind worries and becomes obsessed about these things when I'm depressed...this sucks.