There's nothing wrong with your specs; should be performing great. Sounds like some other process is running on your computer and hogging all the resources. A full reinstall may help, but before anything that drastic, perhaps see if you can identify the offending program and disable it. (Viruses are also notorious for doing this, but the principle is the same).
Also, if the games you are playing are online, it could indicate issues with your internet connection, especially if you're playing over wifi. Any of that apply?