Whats up wih me?

Sometimes I am happy! Other times I am sad and cry! Then I am pissed and yell. The smallest noise gets on my nerves. I feel so BLAH but when I leave the house i put on a smile and prtend everything is ok. Then I return home and back in a pissy mood. I cry for no reason sometimes. I yell for when I shouldnt. My patience is low!