Bi sexual?

Im married a long time, but every so often I get this overwhelming idea to have sex with another female. I havent acted on it yet, but its getting there. My sex life at home was never that great, but am I alone here with these feelings. I have grown kids and if my two boys found out about this I would be ashamed badly. I would not want to be seen by anyone I know, so Im looking where no-one knows me. The thoughts are daily, but doesnt stop me from working. But can you tell me what is going on?