For my CL reversal system, the last 4 months have generated 34 trades (~ 1 every 2.4 day). From June to November 2011, the number of trades for last 4 months was in the 70-80 range (~1 every day). In Jan/Feb/Mar 2011, it was in the 30-35 range (~1 every 2.5 day). From Feb to Dec 2009, it was in the 45-55 range (~1 every 1.6 day). I think this is pretty normal variability.
Most likely your system is impacted by market volatility, or lack thereof. It isn't unusual. Backtest your system incorporating the VIX. Adjust your entry levels based on the VIX and see what comes up. VIX is a major filter in how I trade, and it may be for you as well.
Funny you mention that because I looked back at the dates marking these two distinct periods and there was definitely a shift in the way the VIX acted at that time and the relative decrease in frequency was accompanied by a falling VIX. This is for ES trades. On the other hand, I have been testing a similar system on the Euro for about two months and the frequency in that instrument has been 1.5X what I've gotten in the ES and with a better profit factor. Since the Euro volatility index (EVZ) hasn't really moved, I'm not quite sure why this large discrepancy between the two instruments' frequency.
And the profit factor stayed about the same during each of these periods or was contained within a relatively narrow band?
There is a drop of P/F which started pretty much August 1st 2011 ... does not correlate with recent drop in trade frequency.