Aww I just wanna give you a big hug!! Sorry to hear you're feeling down.
I was going to say that it doesn't sound like you are depressed - just having a bad time of it at the moment. However you did mention you've had postnatal depression before? In that case maybe a trip to the Dr might be in order? I guess they can talk you through it and see if you are actually depressed now.
I certainly have bad days where I just want to run away (for an hour just to catch a breath!), but I don't cry and I'm better the next day. So maybe if you are finding you're more unhappy than happy there's more too it.
Again - I just wanna give you a big hug! So take a virtual one instead.
PM me anytime sweets xx