I recently hired a personal trainer and have been unable to complete even 10 minutes of any of the programs I have been given. I am only 19 years and I remain fairly active (20 minute runs at least 3 times a week), but saying that i also must note that it takes me a solid 2 hours to recover from one of those runs. I have always, for at least the last couple of years, felt dizzy when standing up and had a real lack of energy throughout the day but since starting this program after about 5 minutes of light cardio (running in different directions) I feel very dizzy,enough to have to sit down for fear of fainting, and have bad cramps in my lower stomach, my head also aches slightly. My trainer also noted that my pulse rate is very weak when I am working out, my heart rate was at 86bpm when I was sweating and very tired during cardio. She thought I had something like anemia or orthostatic hypotension however I donate blood and my iron count is at 12 and when I went to my doctor yesterday and did the blood pressure test (lying to standing) and it was normal. Any ideas what might be going on? And should I continue to try and work out? My trainer said she'd try and do even lighter workouts (yoga etc.) However, she said she needed me to get diagnosed before she would put me back on my 'police bootcamp'.
Some extra information if needed: I am female, I have a well balanced diet and I do horseback ride frequently. I have had 3 concussions in my life (from falling off my horse) but its been over 2 years since the last one.