Hi thanks for your question
Your 18 years old and having pain on left side of chest ,left side of neck and left arm,occiosnally on right side.
If this pain would have remained only to left side then,cardiac origin would have No 1 reason but since it is also on right also, so most probably it is not of cardiac origin.
Most probably this pain could be due to anxiety
(tension),So relax and consult a nearby physician to rule out cardiac origin of this pain.
You may need some anxiolytic (tension reducing medicine)
Hope this answers your question