I been having a lot of pressure back of my head along with other side affects. Trembling, dizzy, fatigue (severe), heart racing at times. Mostly this is back of my head. Sometimes taking pain medication over the counter does not relieve the pressure. It isn t a headache, it s pressure as if someone is filling my head with fluids. When my head begins to hurt, I become very tired, and need to rest during the day. This been getting worse for three years now. Do you know what could be causing this?