What Does A Low Reading Of Testosterone Imply?

Hello, I am at a loss as to what is afflicting me, and have been backwards and forwards to the doctors' for almost 2 years now. I am a 21 year old male whose main problems include inexplicable fatigue and mental 'foggyness' (best way of putting it). Other symptoms and characteristics that may be of a note are the fact that i can not grow facial hair, have wide hips and suffer from gynecomastia, although I am otherwise healthy and have a BMI of ~20. My main problem has been the tiredness, which has become progressively worse over time. I have had a mulitude of tests investigating the following which have all come back fine: -Thyroid function -Diabetes -Multiple Sclerosis -Full blood work up I am currently waiting for the results of a sleep apnoea test, and also had a synacthen induced adrenal test done recently although the results are currently lost... I have also had tests done regarding sex hormones, although the endocrinologist I saw reported that everything was in working order. Only possible thing that may be amiss was a testosterone reading of 12 nmol/l (345 ng/dl) which I myself considered to be low for my age, but was instructed that anything between 10-40 nmol/l is within normal range and that every person is different. Should I pursue this further, the gynocomastia is getting worse. There is no hard glandular tissue, and is instead rather 'puffy' and in a shape that protrudes like a cone. My areola are also rather large for a male although not exceptionally so. Adipose tissue around my breast area and hips is disproportionately excessive considering I am of a slim build (little muscle, narrow shoulders). Could testosterone levels in the range of my results cause the symtpoms I have listed, especially the tirdness/unrefereshing sleep/lack of mental acuity? I am at a loss and any help or opinions would be much appreciated. Many thanks in advance