You could be a 'rapid' cycler, but you can also be 'bipolar II" which is a lot milder than 'Bipolar I'. But you do not want to ahead of the doctor and self-diagnose yourself.
I have a lot of mixed-states (Bipolar I), and from what you describe of your symptoms being a few days. I would have to say it might be something else. My mixed-states last longer than a week, probably more like a few weeks. It is usually a state of mania and depression all mixed up in the mix.
Rapid cycling, is if you have your symptoms 4+ times a year. A few good days, ending in a crash that is a few days long too. This is the hardest form of bipolar to treat.
Bipolar II/Hypomania is when symptoms are milder than Bipolar I, but should not be ignored none the less. It usually lasts less than a week of hypomania and can follow/or not have another week of so of depression.
I hope you the best on your diagnosis. Please do not feel too discouraged, and know we are here for you when you need to talk.
"Don't let your yesterday, ruin your today"