Far Cry 3 Lag

I have been noticing from a month that my Laptop's performance has gone down drastically. Earlier I was able to play Far Cry Primal at medium settings and 1080p without any lag, but now even Far Cry 3 lags on lowest settings and 720p. What should I do, please help. :confused2::confused2:

A list would be really helpful; Thanks in advance.