Mirtazapine causing anger & irritability.

I’ve recently been prescribed Mirtazapine by my GP and at first I was reluctant to take it due to the risk of weight gain, but after some thought decided that I may as well give the medicine a chance. Anyway, I have been taking this medicine for a few days now and my goodness, the irritability & anger - in fact I would say it is more rage! That I have been experiencing is awful. Anything, the smallest of things are absolutely infuriating me, I’ve lost all of my patience, I’m blowing my fuse constantly & if everybody even try’s to enter my personal space I literally explode. Sleep wise, well the first night I spelt for 12 hours, but since it’s just been back to the usual battle to fall asleep & I’ve actually been waking up earlier than I usually do. I don’t think this medicine is for me, I’m being a horrible person.