Muse, that sounds a bit like what happens to me. I made a post about one of my experiences a while ago here . I was convinced it wasn't a panic attack, that I was just overreacting, but when I told my therapist about it he gave me a sheet with panic attack symptoms and asked me to tick all of them that I had...four or more was a panic attack, and I had seven!

I noticed you were asking for help without therapy - well, one of the things my therapist showed me how to do is diaphragmatic breathing. http://en.wikipedia.org/wiki/Diaphragmatic_breathing - there are some links from that site. It's been very useful, and not just for actual attacks either - it helped me relax a bit before my French speaking exam!