I went to the pool 8 hrs ago. I haven't went swimming many months ago. I have a really bad headache. Could it be the chlorine or something else?

Could be the trigger. Chlorine and other chemicals used for cleaning/maitaining the pool can trigger a migraine headache etc...Excessive chlorinated water up in the nose during the swim probably was the culprit, or it could just be coincidence. If you never had headache before, and if this does not get better, consult doc... Oct excedrine etc.. May help... Good luck..