Hm, you could get yourself tested to put an end to his petulance... or challenge his conviction by playing up to the assertions (some 'stick on' tattoos, fake nose ring...) to help him see the nonsense of still treating you like a child.
He has been the 'alpha' in your life and it must be hard to let that go. Perhaps some kind acceptance and a little understanding - he is free to believe whatever he wishes, fact or fiction; and I assume you still live at home, so a little extra leeway is probably in order until you step out on your own?
Although it is hard to hear parents talk down to you, how you process those words can lessen the impact - scoff at the foolishness, echo the comment in a 'return allegation' - all equally ridiculous, but he might just catch on. The damage is the extent to which you are taking this to heart - he still exudes power over you until you rise above.
