If your attacks are lasting all day, then it most likely is not a panic attack. Panic attacks only last for a few minutes- they have an abrupt onset, and are random and spontaneous. Panic attacks come and go, and generally lasts 5 to 15 minutes, then it vanishes.
If you are having attacks that last all day, you may be experiencing chronic stress, that is the result of chronically activating the fight or flight response. When your stress response is constantly activated, then you may have physical symptoms such as increased heart rate, muscle tension, sweating, and tremors, just to name a few. So you have to address what is causing you chronic stress, and then you have to decide on increasing your coping skills and/or engaging in relaxation techniques.