USDJPY BB backtesting

I tried to backtest the bollinger band indicator for USDJPY.

This is how I use the bollinger band
1. Buy when the price close or touch lower band and close when the price touch middle band
2. Sell when the price close or touch upper band and close when the price touch the middle band

For now, 40 trades I made and total pips gained is -332.2 pips.

I really appreciate if you can tell me how to improve the results.