Agree that unilateral headaches are often igraines- and workouts change hormones=change neurochemistry.
However, as you're lifting weights, it wouldn't be a bad idea to call your doc and check in- headaches can also be caused from neck injuries, brain bleeds, etc. (not to frighten you!)- but why risk it? Get a good checkup and make sure to ask questions about your headaches- are you taking meds, herbs, steroids, birth control, etc.? Talk about EVERYTHING so the doc can put a picture together-
I hope you feel better xoxox
Nicole
usually a headache on the one side of your head is a migrain,which can also make you feel sick and tired.