In my sharepoint designer workflow some steps needs to be repeat when the condition goes false. How can I do this?

SharePoint Workflows are weak, especially in this situation.  But, you could make a seperate workflow, then have it called in multiple situations.  Of course, in 2007, you'd have to install codeplex's SPD Activities to get the "Start Another Workflow" action.

So, the answer is probably... just grunt through it, and duplicate the code for the False condition.

If it is a SharePoint 2013 workflow that you are creating, you can create an additional SharePoint 2010 list workflow containing only the steps which are repeated and call the 2010 workflow from 2013 workflow, whenever condition goes false using 'Start a workflow' action.