You are always bi I think, it is just what you prefer at a certain point in your life. You may have a stronger preference for women, but even if the attraction to men is few and far bewteen, I'd say you're bi. I'm definitely bi, though I married a man, but he knew when we go together from the get go. I just could never see myself in a long-term relationship with a woman, though maybe I never met the right one.
Being bi is ok, it's just the issue of being faithful, or honest about it and if you do have a third party involvement that everyone is comfortable. Some people even have tri-relationships (not recommended!!)
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