Can you help diagnose light-headedness, blackouts, muscle fl

I’m a 20 y/o male with no past medical Hx. Approximately 5 years ago I went to see my local GP because I was experiencing light-headedness and blackouts (with nil LOC) quite frequently, particularly during exercise. After several examinations from different specialists I was told that the most likely cause of my symptoms were due to postural changes in my BP during exertion. It was noted however that my vitamin B12 levels where low-borderline (but I was not told this had nothing to do with it). The 5 years to follow saw me have an increase in the number of symptoms I had albeit the blackouts seemed to have just ‘grown out’ of me. The symptoms were, in order of how I remember they progressed: Muscle fluctuations, rapid muscle fatigue and weakness during exercise, tiredness, paresthesia (particularly numbness in my legs), SOB during mild activities, memory loss and tension headaches. After returning to me GP, a blood test found that I had allowed my vitamin B12 levels to drop to 62 over the last 5 years. To reverse the deficiency I was given the relevant injections over several weeks until my levels came back into the norm (now 500). For some reason however, and beyond the knowledge of my doctors, my symptoms have remained even after treatment (particularly my muscle twitches, memory loss and headaches). I have also noticed that I have been getting quite depressed and emotional lately.

Before you ask, I am not a vegetarian. In fact I love my meats, and all the sources of vitamin B12, so I can assure you it is not a diet induced deficiency. Saying that, I am not overweight, I’m 6’4” and weigh 95 kgs, and I don’t believe my SOB is caused by a lack of fitness. In addition we have ruled out SOB secondary to anaemia as my haemoglobin counts have always been normal. My doctor says that I might have been born with the inability to absorb the vitamin… however I wonder why I have been fine for at least 15 years of my life. And while I understand that my symptoms could mimic several underlying pathologies, I was just hoping someone could read my story and think outside the square. Perhaps the first thing that jumps into their head. And by the way, I would like to say that my symptoms (all of them) are not chronic. I can live with them just fine. I would just like someone to help explain why my legs go numb after not moving them for 10 seconds and why I can’t remember locking my car immediately after I’ve locked it.

thank you,

zneh2