I've had an anxiety disorder for about 4 years now, generally it can be "triggered" by something, some life event, other times it can just come over us for no apparent reason, but there could be an under-lying reason that you can't actually identify yourself.
These anxiety attacks are exhausting, especially when they are so frequent. When mine were at their worst I was off work with it and would have to just lay down till my heart returned to it's normal pace!
I would recommend you see your GP and a counsellor for some "talking therapy" to see if they can unearth an underlying cause.
Also a beta-blocker tablet can help with your racing heart, like propranolol or bisoprolol which is what I still take now, 4 years on.
Some anti-depressants also have anti-anxiety effects, I take Venlafaxine 150mg every day.
Sometimes this combination of tablets is all that's needed but mine spiralled out of control 3 years ago due to family worries and work stress (nurse Practitioner) I was issued with some Lorazepam 1mg, which helped me get back on track.
My anxiety is well controlled now but I know it's still lurking! So I try not to get out of my "comfort zone" !!
I would certainly advise you see someone about it, get it under control before it spirals and gets bad like with me as it made me feel so ill.
Some counselling/talking therapy maybe all you need but medication can certainly help and I would recommend this if it's offered to you.
Don't try and cope alone, I did this for months and in the end it made my recovery longer.
I'm so sorry you're feeling like this, I remember it very well, that racing heart, nausea, rapid breathing and feeling faint is awful beyond words, I'll never forget how it made me feel, so please get some help, I just wish I had sooner than I did.
I tried relaxation CD's and calming breathing, which does help too, but get advice.
I'm happy to chat anytime, I've been there but the only way I got through it was to get help, coping alone was not working.
Thinking of you and please keep in touch,
Love Lucy xx