I agree with the other posters...just try to keep an eye on it. Stimulants aren't for everyone, but many people do benefit from them. Addiction/abuse/dosage escalation can be an issue, especially with the amphetamines (ritalin, I think, is supposed to be less abuse-able...), but still: if it helps and the adverse effects aren't too terrible, I'd say just keep on takin' it.

I don't think hypomania is always a bad thing, anyway. I think it varies from person to person. Some people get more done during hypomania and enjoy the feeling. Other people have so much irritability and such that they can't stand the hypomanic episodes. I think maybe you should try to avoid over doing the self-monitoring. Its good to be self-aware, its good to be cautious (especially with controlled substances), but not every up and down and in between is an "episode" of any sort.