Cost of equity query

Hello everyone, I m a newbie who had a query. I was calculating cost of equity 4 few companies last year. I was using the CAPM formula. Now since markets were falling continously around this time (Sept) last year, the returns of the market were less than the risk free rate and there was no equity risk premium giving the overall cost of equity a negative value. Now i undertsand that a positive cost of equity is incorporated in the WACC to work out the discounting rate. A negative cost of equity implies the opposite and would mean that the stock is going to fall further. However how do I ascertain the WACC in such a case. I had this query for over a year now. PLzz help