I went to personal training and told the trainer about my symptoms. He adjusted the exercises so that I was always sitting or reclining, and never changing position during one exercise. Everything went very well and my symptoms didn't flare up. Afterwards I did low speed, low intensity rowing and that is when a weird spell of lightheadedness and even a feeling of extra warmth in the head surfaced. I stopped rowing after 20 minutes because of those odd and unpleasant sensations. Still, more than 1 hour activity time today. I hope these symptoms do not recur during cardio, and if they do, I will definitely seek medical advice.