Hi I'm a 21 year old guy: I weight 164 pounds and I an 5.6 feel tall. I don't have any medical history relevant to this problem. Yesterday I went to the gym and I started doing exercises for my back. After the first 2 sets I felt my head spinning, like when you have low pressure. I drunk some water and I went to measure my pressure almost immediately (it was 118, 78 - I'm not sure about the second value...) I felt almost good for the rest of the day. This morning I woke up and I felt my head spinning again, now with a vomit feeling followed by it. I drunk water. I ate something, but it's still there. When I walk i have to be very careful not to hit doors and walls cause I feel i can't walk straight nicely. I already had this in the past even before I started going to the gym. I would have woke up and I would have had the same exact feeling: head spinning and some sort of nausea. What could it be? If it's not pressure and neither dehydration?