Oh I have gone through that- the what if questions; 'what if I did this....' 'why didn't I see it?' you can't beat yourself up with these questions cause you'll build a picture which isn't the real image.
First loves can either be well remebered or end horribly. Heck mine did lol! But depsite my hurt, i'm laughing it off cause I can;t let it get me down; life is open to us both, my friend.
Some partners hide stuff purely for either protection, embarassment, shame, etc. And the fact he didn't tell you after all these years suggest that maybe he just didn't see it as a major problem to tell you. It is in a case of health, and that it's disobeying trust. But i'm sure that you can work this out. He can't let you go after so many years; it's almost impossible; even for the person who has a heart of stone.
Keep strong hunni,
kitty
:)