The neck is intimately connected with headache, and can cause either referred pain to the head, primary muscle contraction/tension headache or can trigger migraines. The neck can also result in dizziness or vertigo as there a lot of sensory nerves there controlling balance, and which way your head and eyes are turning etc.
Lifting heavy weights could potentially out more strain on the msucles of the neck, if its not a favorite pastime you might consider cutting down on it. Lifting weights also causes a valsalva effect - increasing pressure in the thorax and potentially inside the head.
Good luck