Macbook pro running slow, then won't reboot

Hello,
I edit using Lightroom and Photoshop and I'm having an issue while editing. After editing around 8-10 photos in Photoshop the computer starts running unbelievably slow. After each 8-10 photos I have to close down everything and reboot. Even the reboot process is super slow as I have to force quit each application usually 1-2 times to get it to close. Is this normal? I have a 2011 17" with 2.2 GHZ i7 with 8GB ram. Is there any setting that I can change or be aware of.
Thanks,
Jack Fussell

Download "Free Memory" from the mac app store. it displays the free memory available and gives you the option to free the memory. See if that helps you.