At the beginning of a strenuous workout at the gym (Had just done 5 minutes running, 5 minutes rowing, squats, and pull-ups) I had this odd feeling in my left ear. It was as if there was water in it and I felt a bit dizzy. I tried to pop it with no luck.

Within a minute I felt nauseous and started walking toward the restroom and then had to sit down as everything went black. I did not faint, but I had to sit there for a while.

Couple more details: checked my blood pressure as soon as I got up and it was 98/72, I was sedentary the whole day and then started this workout, I ate a bagel with avocado right before working out, I'm not feeling sick and I'm not pregnant, I could have probably drank more water beforehand, and I'm a 27 year old female in decent shape.

So my questions: Is the feeling I had in my ear related and if so, what was it? Is there anything I should be worried about with an episode like this? Is there something I can do to prevent this from occurring in the future?

Thank you very much in advance for your help.