Aww I just wanna give you a big hug!!  Sorry to hear you're feeling down .
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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 .
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PM me anytime sweets xx