Earned Value is cumulative; that is, it incorporates any baseline changes made during the period of performance. If cost was not incorporated into the baseline from which EV is calculated you have a problem. You would have to rebuild the schedule and its associated costs from the beginning, then apply actual costs and status (% completions) to each prior period (monthly, weekly).
Are you using an EV tool, or are you calculating EV manually? Do you have all the backups of the schedule after each baseline change?
It is possible to calculate EV outside the schedule (IMS) in Excel, for example, but you would still need resource rates and actuals and status for prior periods – thus you could estimate the EV.
This is a complex question requiring much more than this simple answer.