To what degree does fertility decrease with age in men?

I'm in my mid 20's (will turn 26 next month), and I'm seeing an older man (in his 50's) - I know, big age difference, so reserve judgment. We use condoms for birth control, but I'm still thinking about going on the pill to have something more reliable. I know that men don't lose their fertility like women do, but I've read that their fertility decreases remarkably at age 35. I read an article about a 40 year-old woman who was having trouble conceiving with her 55-year-old husband. The doctor said that at age 55, most of his sperm were shot, so it would be difficult. I'd never heard that sperm could become less potent with age, so I wonder if it's true. Women's fertility goes down remarkably at age 27, so I doubt there is a high likelihood that we'd conceive even if the condom failed. I do fear that if I got pregnant, he'd leave/fight child support since he doesn't want kids at his age. At our ages, esp. with his age, pregnancy even a real concern?

Also, my bf has erectile problems - he can sometimes get an erection naturally, but often needs to take medicine to help get it up. So does this decrease the likelihood of us getting pregnant? BTW - no, I do NOT want to have his baby. I don't want a baby, and cannot afford it w/o going on assistance if he bails.

I've been in a similar relationship. I've known men in their early sixties who were able to naturally impregnate a woman, so I would be careful.

Basically, the reason some me have problems at that age isn't their sperm, but their functionality. As long as he can get an erection, and my guy couldn't, yours is able to knock you up.

lucky guy

Probably the typical man hits the wall around age 26 as far as getting bigger and stronger. The main hormone that controls the master switches on growth is HGH or human growth hormone. This starts to decrease with age and by the time a guy is 40 it is way down from his teens. But men even into their 70s and 80s can still get women pregnant.

I wouldn't worry about it if you want to have this guys baby their is only one way to get pregnant: SEX. Lots of it. What a problem to have.

I met a couple in May, he was 70, she was in her 30's they had a 10 month old baby....so YES pregnancy is a concern.