You can control mood problems and mental illness in general through medication or will power but the latter doesn't work as good, you can always feel the problems looming in the background and it breaks free easily. I don't know if through practice it would get better or not because I didn't have enough time to try this as I got back on medication. As for medication they have to experiment and find the one that works right for you. It would be best if you spoke with a psychiatrist and figured out if there's an underlying medical problem causing your mood swings.
I agree you need to talk to a doctor. Controling bipolar mood swings is not so simple. Meditating and deep breathing only take you so far. But since you do not know if you are bipolar or not you need to find out. Ask for help wherever you feel comfortable, but that is the first step.
That might very well be rapid cycling. It would be best to speak to a psychiatrist and they could see how to best diagnose and treat it.