What Causes Chronic Panic Attacks?

i am 19 year old male, for many years i have exsperienced aprehension or panic attacks (usally something im looking forward to) over the smallest of things genually! the physical symptoms come and go genually in the sequence, hand trembeling , then leg tremeling, tightness in stomache growing very tight, then causing nausia and then throwing up in some cases (in some cases muscel twiches usally small ones around the eye). which due to the smallness of the sitmulus eg. seeing friends, catching up with friends, before an interveiw, at work if im asked to look after a friends child for a shot period of time. they usally last around 10minuts start to finish sometimes as a cycle, then go and im fine, i have tryed controlling my breathing, cutting out caffine, sugars, saying to myself this is rediculus. starving myself, but the no or little effect. they seem to be getting worse and harder to hide them, so i would like any help or serjestions. its like my body is over reacting like mad and dumping enough adrenerlin to last bloody years. any help? or ideas