Panic Attacks Support Group
A panic attack is a period of intense fear or discomfort, typically with an abrupt onset and usually lasting no more than thirty minutes. Symptoms include trembling, shortness of breath, heart palpitations, sweating, nausea, dizziness, hyperventilation, and sensations of choking or smothering. Panic attacks can be very sudden, appear to be unprovoked, and are often...

What you are having is called "Anticipatory Anxiety", or fear of what MAY happen. This happens to me as well and it is difficult to control. While worrying about something like this is normal, over thinking about what MAY happen is not productive and not healthy! But believe me, I completely understand how you are feeling.