The criteria for a hypomanic episode requires a minimum of 4 days. Some people do rapid cycle but you need to have met the time requirement at some time. Have you looked up the DSM-IV (or even the not yet published 5) criteria for Bipolar II?

Also Substance-induced episodes do not count as part of bipolar. Although antidepressants can push you into a hypomanic or manic state, this happening isn't part of the criteria for bipolar.