I think that is normal. I'd talk to your doctor about it if it seems to be taking over your entire life but otherwise I'd just try to focus on the happy things...easier said than done I know
Its important to keep a good temperature on your mental health though and to let your doctor know about anything that could be a warning sign of PPD. Maybe try to mark off some time for yourself on a regular basis (massage, walks, yoga, whatever zens you out) and make it a priority to take those times.
Good luck
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