Is this bipolar or not?

There are days that I feel suicidal, and then there are days where I can't fathom the thought of even dying. It's like one day I actually debate whether I should just take my life, and other where I am feeling normal, not sad but not happy. It's been a week and my feelings of sadness have not come back. I can hide my sadness at work, actually I am known for being a nice and happy person but when I am alone it's the complete opposite, but like I've said the feelings of sadness have not come back for a week. For the last couple months it's been on and off. Also, when my parents' ask me questions I answer them with annoyance for no reason. Why do I feel like this?