oh, you poor thing :(
One thing i can offer is to think to yourself its "only anxiety"
That sounds really patronising but think about it - what is happening to you at that moment in time (even with the flashbacks) is anxiety. Sometimes when i get anxious i feel like im going to implode. But i never do. The reason for this is what is physically happening. The triggering thoughts are causing you to become anxious, as a response to this your body is going into fight or flight. Lots of adrenalin, cortisone and other hormones released and it increases the feeling of anxiety, but after a while the hormones reach such a level that they start to switch themselves off. Every time, it happens that way - the panic subsides.
So its a way of taking control, its "only anxiety" it will pass, i am safe.
Of course it isn't "only anxiety" in terms of the effects it is having on you.
Are you getting help? You say you have diazepam, are you on anti-anxiety meds other than this? Diazepam is only a short term fix and to be honest, i didn't find it helped very much at the low dose i suspect you take.
You mention flashbacks - are you getting help dealing with this? Do you want to discuss it here? I understand you might not want to.
I have discovered running, my anxiety is terrible at the moment, i don't often have panic attacks, its more like there is one constantly brewing. Running really really helps - despite me making 
faces at the dr when they suggested it, i cannot believe how much it helps. Doesn't have to be running but another type of exercise - even walking will help with hormones and also distraction.
Hang on in there - remember its "only anxiety"