What's up with my MacBook?!

The other day I plugged in my old SD card from my camera into my MacBook pro, and ever since I uploaded those pictures, my MacBook has been running suuuuuuuuper slow! I tried deleting the pictures, didn't help. So I looked and saw I had an update! So I downloaded the update and then when it restarted my computer, it never got past the grey apple loading screen when you turn it on! I did this about...5 or 6 hours ago!!!! I'm so frustrated and it won't turn off or anything!! HELP ME!!!!!! I've never had problems with it before:\ and while it was being slow earlier, it would pause and play my iTunes music and it took about 5 minutes(or more) to log off of each app! What's wrong:(