Hello, what are your system specifications? is the OS Windows 7, 8.1 or a Mac? What are the specs of your processor and video/graphics card? Also, what was your ram total before upgrading to 10GB? Do you know how much ram your system can take? If you have gone over the maximum limit (say, 8gb is how much it can take and you have 10), it can not run properly and may strain more of the CPU in your machine. If it can handle 16GBs, than its not so much the ram but likely the video card (if you upgraded it or not) or the processor.
One more thing, what quality settings were you running it on? Did you change any game quality settings before and after changing the ram?