I m a 26 year old male. Suffer from constant back pain , work outside in the heat. For about 3 days now, when I stand up from lying or sitting, I get severe pain back of head. Dizziness when standing for extended amounts of time. With the dizziness comes slight nausea . Just yesterday, I began feeling slight pressure in my sinuses. Went to a local clinic. They gave me some sinus medicines and antibiotics, but didn t really tell me anything. The did say that I had a low white blood cell count.