Last Week I Started Getting A Throbbing Pulsing Pressure On

Last week I started getting a throbbing pulsing pressure on mostly the left back side of my head (slightly towards the top), and I've had it on and off until now. When I bend over or move suddenly it gets worse. Sometimes the feeling moves to the right. Sometimes my neck, but mostly the left back top sid. Sometimes I feel pressure around my eyes. After a hot shower it feels far worse. Deep breathing seems to make it better momentarily. I've had this same sensation before, when I'm dehydrated or can't breath well through my nose. I've taken a lot of antibiotics in my life. Could it be candida? Anxiety? Sinus issues? (I had a nasal polyp removed 6 or 7 years ago, but I can't breath again from my nose very well). Something far worse?