Sounds like you need more ram. when you play a game, if you have it set up to run on the gtx, the integrated graphics will turn off automatically. Many games require you to set the gpu you want in the NVIDIA control panel.

1:Open Nvidia control panel, 2: select the program settings tab, 3:There is a list of programs to customize, select the program you want, if it is not in the list, go to step 4: Select add, and then it will give you a new list of programs to select from. 5: Once you selected the program you want the tab below which is numbered 2. You can select integrated graphics, or high performance gpu. 6: Hit apply.

This will make the integrated gpu be disabled when the game you are playing is on the other GPU.

Hope this helps.