Over the past 6 months, i have gone from 170lbs, with very little body fat, to 155 pounds. I probably lost 20lbs of muscle, and gained 5 lbs of fat. This didn't happen fast either. I have just been slowly losing 1 pound every week or two, even though nothing in my life has changed. I have not been 155 for about 3 months. I have no energy anymore, and no motivation. I have absolutely no libido, and cannot ever get an erection. I am 20 years old and this is supposed to be when I have to worry about these things the least. When i was 14 I had a condition where i couldnt start puberty without a series of shots. My father also had the condition. My father also was diagnosed with very low testosterone levels in his 20's, and has been on biweekly injections since. I am going to my doctor in two weeks to discuss this. I am pretty sure low testosterone is my problem, and i really want it fixed. Is there anything else you recommend I say to my doctor? He seems pretty old fashioned and un-willing to believe a person of my age could be suffering from this. But since a year ago I have taken a complete 180. Any tips/help would be appreciated before i see my doctor or do any bloodwork.