I keep getting pain in the back of my head. It feels like pressure. Do you know what it could be. I have low blood pressure and wpw?

Anything. Headaches can come from fatigue, sleeping too much or too little, sleep apnea, snoring, being dehydrated, having chronic sinusitis or allergies, too much caffeine or over the counter headache medication, high blood pressure or something more serious like a tumor. See your doctor and get checked.