I have a few suggestions.
Put a waterproof mattress pad on his bed, and accept that you'll be washing stinky sheets every morning.
Put a "Goodnight" pair of absorbent underwear on him at night (some kids don't have good bladder control, and are bedwetters until much older than your son, so there are products on the market to help)
Take turns with your husband getting up with your son at night to use the bathroom. No, it isn't fun, but if you give it a couple of weeks, he might be able to get up on his own and use the bathroom.
If he's having accidents during the day, try reminding him to use the bathroom throughout the day. At that age, they get so busy with all the exciting things they do that they don't want to take the time to use the bathroom until it's too late.
Have another talk with his doctor. Urine that smells that bad doesn't seem normal to me, and now that it's been going on for awhile, maybe the doctor will have some ideas (other than a UTI) for wht is causing it.