Have been with my partner 20 years he has just turned 40 and this has never happened before but six times in the last three weeks he has gone soft just before sex. Previously hard and then out of nowhere just loses it. Nearly every time he has got it back and we have carried on. Just wondering is this common? He is a heavy smoker recently started again after giving up for 10 years.could that be contributing. Is it his age? Any advice on how to deal with this please.