I cant seem to find what is blocking my camera saying another application is using it.

The FaceTime camera can be used by one application at a time. The message, "Your camera is in use by another application" may appear when you try to video call.

If you receive the above message, follow these steps:

1. Quit all applications that are using the FaceTime camera. If you don't know which applications might be using the FaceTime camera, quit all open applications. Examples of some (but not all) applications which can use the FaceTime camera include iChat, iMessage and PhotoBooth. 
2. Open only one application and use the FaceTime camera.
3. If the issue persists and you are using an external camera, unplug the connecting cable from your computer and the camera, wait a few seconds, and then firmly (without forcing) plug the cable back in to the camera and the computer.