Feeling extremely anxious tonight....

My nervous have been playing havoc all day. All day i have been fighting myself . I hate it! I was at the dentist today and thought I was going to have a panic attack whilst in the chair. i told them that and they were pretty good in understanding. I breathed my way through it. I just relaxed my body and did slow breaths. Tonight, though I can't shake it. But mind u this is when I feel most anxious (at night). It scares me most that I will wake up to go to the toilet and then I will have one.
All day long I think about my panicing and then as soon as i wake up. That's the first thing i think of... Am i going to have a panic attack??!! I need to change the way of my thinking.