Hi, welcome to the forums! It's very difficult for us to know what's causing your device to run slow if you don't give us more information. Check in your battery stats if any app is taking an unusual high percentage. Also, do you have any cleaner, memory booster or battery saver app installed? If so, uninstall it and see if it makes any difference. And, if you fancy that, a factory reset will probably help.
I recommend you to create a free account here at Android Central so you can reply in this thread and we'll try to help you out.