I am having a pressure feeling in me head with dizziness & nausea. I also have a stiff neck but no headache. This started 3 days ago. What can it be?

Many things. The symptoms you describe can be due to MANY things. Some benign, some concerning. Best to see doctor for evaluation to help sort out if this is something that can be watched or needs further testing and evaluation. Sorry this is not more helpful. Best of luck. Dr R.
Pressure. These are vague symptoms. Get your eye vision checked. Or you may be have eaten wrong food which you could not digest properly. You may be tired, exhausted, or stressed, so take some rest. If symptoms persists and increased., please see your doctor.