How do I control my severe mood swings?

Lately I’ve been having terrible mood swings – I’ll be completely fine and then in a matter of split seconds I get extremely irritable, cranky and basically turn into a nasty bitch and feel like screaming and crying… sometimes I do. It happens at least once a day and lasts the whole day once it happens. I’m on 20mg of Prozac and 15mg of Mirtazapine so they must not be working well. I have no idea why this is happening and I will be going to see my doctor soon but for the mean time, how do I control my mood? My family and friends are getting pretty upset with me.