I was stung by jellyfish had a reaction which has returned. Along with head ache ear and arm pain on my left side only could the pain be from stings?

How long after? Although most jellyfish sting pain is acute, there are some cases of delayed/recurring reactions days or weeks later. http://www.ncbi.nlm.nih.gov/pmc/articles/pmc2380397/ sea-bather's eruption is an example, where the nematocysts (the stinging parts of the jellyfish) can remain in swimsuits and cause a reaction when the person puts his/her bathing suit back on. If longer time gap, another cause.