It does sound like Anxiety some things to try
Breathing exercises, Learnt this one at a depression workshop was to breath in and hold the breath for 6 sec then breath out for 9 sec. I find abdominal/diaphragmatic breathing works better for me, it's the type of breathing babies and infants do before they really start using the muscles between the ribs as adults do.. It's not as easy but it works on 2 levels first by using the diaphram it takes less effort and the lungs fell more effectivly so reducing your heart rate, at the same time it also sends messages back to part of the brain using the autonomic nervous system saying everything is OK so reducing your adrenaline production. You will probably need to practice this regally normally they recommend 3-5 times a day for 5 mins. There is an explanation on how to do it here walking.about.com/od/fitness/a/breathing.htm and you may want to look up things by Dennis Lewis (he's a bit cheesy mind)
Physical relaxation - It's a rare person who can just relax often it's easiest to start at one part of the body tense the muscles then relax them I start at my toes and work my way up, I have also been talked through tensing everything holding then relaxing, sometimes it's easier doing it with a voice telling you what to do There is a free one here you can download onto a MP3 player Living Life to The Full www.livinglifetothefull.com it's a CBT course it's free maybe something else you find useful as they have a section on anxiety. There is a basic relaxation description here www.brianmac.demon.co.uk/relax.htm
Visualisation there are probably many forms of this I the one one of my counsellors did was to imagine I was on an island he asked me what it looked like trees, birds look inland what did I see (I saw a river followed it to a pool and waterfall sat down and point blank refused to go any further) My safe place visualisation is now the pool and waterfall. I have found one free online course that describes it's self as guided visualisation www.success.havemorefromlife.co.uk I used a random email programme www.temporaryinbox.com so I don't get spam (I never trust things like this)
There are also several techniques used here www.twu.edu/o-sl/counseling/SelfHelp039.htm
Self hypnosis I know nothing about it but someone else might
With all these things it's practising that's important normally they recommend you do it 2-3 times a day when you get up, go to bed and sometime during the day if you have time. Something like the deep breathing you could do on the train on the way too or from work or sitting in a traffic jam... Visualisation and relaxation not as easy to do it somewhere where you would be self contions