Personality or Bipolar

Today I sat in my closet and cried for an hour. I don't know what is wrong with me. I feel like I have been going through this for 31 years. There are times when I am the happiest person in the world and I just have fun with my family. Then there are times where I would lash out or just start yelling about the simplest things. I hate this feeling. I feel like it is destroying me. My children feel that I am bi-polar and it is sad because they are aware that something is wrong with me. I spoke to a doctor about this maybe 2 years ago and she said I couldn't be bipolar. However, I am feeling that something is wrong. Everything irritates me. I can't stand when people chew food loud, i can't stand when people wiggle their toes, I can't stand when someone stares at me. I just don't know whats going on. Just typing those things that upsets me made my stomach hurt. I'm afraid that no one is going to want to deal with me ever. I thought about just leaving my family so that they don't have to deal to me. I have 4 children and I know this would hurt them, but I feel like my traits are rubbing off on my son. Does anyone suggest I get a second opinion?