Sounds like you need the right anti-depressant. I began to worry that I was going insane when I started having constant violent, homicidal and rarely suicidal thoughts and images continuously pop into my head. You said you've been on medication? Maybe you haven't found the right one. I was never depressed and I myself, like you, live an incredibly active and healthy lifestyle. My doctor diagnosed me with obsessional thinking, gave me Effexor, and pop! It's gone man. The relief is orgasmic. You should listen to Dr. Rob, though, it could be organic. From personal experience though I can tell you what my psychiatrist told me: "It's your extreme anxiety battling with your admirable self control, detouring around it to manifest itself in completely bizarre ways.
The feelings of unreality, too man, I had those too. They went away, as well. Believe it or not man it's just anxiety, trust me on this. Go get yourself some anti-anxiety meds. Effexor works miracles for me but I understand that's not the case for everyone, so ask your Doctor to begin trying new meds and maybe some therapy.
Trust me on this man, it gets better, you're going to be ok.