My mom and I are constantly arguing and it's very emotionally draining. She always initiates the fights and then blames me. I used to get more upset and yell back, but recently I've been very cool and collected. I'm wondering if she has bipolar disorder or something along the lines of this because she gets depressed and then happy and then screams at me. Sometimes this all occurs in one day. How can I diagnose this and how can I try to talk to her about it?
Mental health issues are not generally good do-it-yourself projects. As cdnreader points out there can be many causes for your mother's behavior. After you know what the cause is, read up about it. Come back here and ask who has dealt with it. The doctor and experienced caregivers here can help you figure out how to deal with this. But first you have to know what is going on.
Best wishes to you as you work through this.