I know a guy who has never ever reached an erection again after using benadryl and it's been 8 years since then. They were desperate for a child, so eventually he tried taping a pencil to the goods. No luck though. After 3 years his wife got a divorce and his gf had left him only a few weeks after he had acquired the disability.
It's a sad story really and all my empathy goes out to you, dark wolf. You should look on the bright side though: You will always have something to remind you to never ever dose 650mg of Benadryl again!