Have you been to see your Dr about what's going on? If not, I would recommend doing so. What other symptoms are you having and have you ever been diagnosed with anxiety before?
I do know that anxiety does not have to have a cause - it just can happen. If its been happening the last few months, you need to go see your Doc.
Another thing to consider is something like ADHD/ADD. Since you feel these things at work where there is more stimuli, I have to wonder.
You may look in to your personal life too and think about what is stressing you out. Sometimes certain times during the day (and maybe this is work for you) is when our brains try to process that stress.
In any case, go see your doc and be honest. Keep a journal of what you feel and when for a little while so that you have some solid information the doc can look over. Its good to record exactly what was happening before you began to feel anxious/sick/heart ache.
I hope you feel better soon.