Overwhelming emotions

I don't if it's mood swings, but I'm constantly under the grip of strong emotions. I might be very sad at one point of the day, and furious the next moment. It helps to talk to others about it, but I still don't understand why this happens. I don't recall being like this a few years back.. it feels like I've become more whiny about my problems too, and I'm not able to deal with it. I've tried breathing exercises and mindfulness, but I just can't seem to control myself at the heat of the moment. I'd really like to hear any advice.